Hi Steven, let's take a look at your game.
I think I had a quite good early and mid game.
You had a strong early game and solid map control. However, you failed to capitalize on it during the mid game and let your opponent get back on even footing. This happened because you didn't invest in fire support units (mortars/snipers) and you lost your vehicles.
When you rely on vehicles like the Half-track with Flame Projectors to attack enemy defensive positions, you need to be very careful about microing and supporting the attacks with infantry. Rather than send your Half-track way around the back on its own, and lose it to AT grenades, it would have been better to send it straight toward the Maxim in the building to clear the way for your infantry and HMGs to advance and retake the right side of the map.
Once your opponent had two mortars, an AT gun, a Maxim, and several infantry squads all supporting one another, the safest thing to do is invest in fire support units yourself. For example, you could have used a single mortar to lay down a smoke barrage, allowing you to rush in your infantry without worrying about the Maxim. Smoke barrage would also have been useful in attacking with a Half-track, supposing it were still alive or you had rebuilt it, which is always a good idea even if you can't afford the Flame Projectors -- field reinforcement is very important. If you had picked the Joint Operations commander earlier, you could have called in an Artillery Officer (for smoke barrage, to boost your infantry effectiveness, and to use in conjunction with mortars). Alternatively, in the game position you had around 8-10 minutes, I would have picked Spearhead Doctrine for one or two Mortar Half-tracks. You had a major fuel advantage and their Incendiary Barrage would have easily cleared out the Soviet position on the right.
Because you had such an advantage in fuel, you could have safely built an Ostwind first, which would have easily controlled the left side of the map on its own, and could have been used in an assault on the right in conjunction with other units. If you don't have to worry about an early SU-85, which your dominant early game ensured, an Ostwind is a safe decision and clears out infantry more rapidly than the Panzer IV.
Losing the second Panzer IV on the right was also a major problem, and this nullified your early advantage even further. By 18 minutes, the game was fairly even when at 8 minutes you were dominating. Most significantly, as your opponent was able to hold onto his fuel without teching to either Tier 3 or Tier 4, you ran into the problem of KV-8s and the IS-2. The best way to counter such a strategy is to exert major pressure in the mid game with light vehicles and tanks, specifically the Half-track with Flame Projectors and the Ostwind.
But in the late game it was really hard. There where many Paks. Ok, that shouldn´t be a problem. But in combination with that f***** flamethrower tanks... it is annoying. I tried it to handle with P4´s, with Panzerschreck-Grens, with a Pak. Finally an IS2 were my huge opponent.
If you see a KV-8, do not buy Panzerschrecks. The KV-8 has a long enough range to melt Panzergrenadiers as soon as they try to fire, the weapons don't deal significant damage to its heavy armor, they're expensive in munitions, and it's likely that your opponent will pick them up. Against a KV-8, you want to damage its engine with a Panzerfaust and then pound it with AT guns and tanks from a safe distance. Beyond what you already had on the field, one Pak 40 would have been a good idea.
The problem you faced by relying on Panzer IVs was your opponent's AT guns. If you had your own AT gun it would have been less of a problem (the ZiS barrage isn't cheap, and you can move a Pak 40 out of the way). Also, if you had mortars or a Mortar Half-track to threaten the AT guns, it also would have been safer to use the Panzer IVs.
After you were able to push back the KV-8 and AT guns around 27 minutes using your Panzerwerfer and Panzer IVs, you had around 300 munitions. This would have been a fantastic opportunity to plant a few Teller mines. If a KV-8 or IS-2 hit one, it would be out of action for a fair amount of time and also easy to destroy with an AT gun.
It's very important to preserve your Grenadiers throughout the game, due to their veterancy and the need for Panzerfausts. It would have been worthwhile to rebuild at least one squad instead of getting Panzergrenadiers as you had plenty of munitions for LMGs if you needed to boost their anti-infantry effectiveness. Panzergrenadiers are superior if you're fighting against T-70s/T-34s/SU-85s, but they're more of a liability against KV-8s and the Grenadier Rifle Grenade is superior to the Panzergrenadier Bundled Grenade in combating weapon teams.
I'm not sure why you built an Ostwind late in the game. It's most effective as the first tank you build. By the late game I would have focused on building Panzer IVs exclusively, and ensuring that you have at least one Panzerwerfer alive because it's the best counter to AT guns you had available (you were rather careless in losing the one you had).
I noticed that your micro/unit control could have been better in the late game fights, read through the advice I gave to NorthWestFresh earlier on in this thread. I think you'll notice a difference.
At 34 minutes when the IS-2 came out you were in a slightly stronger position overall. Your opponent was completely relying on the IS-2 to push you back, and because you had the infantry advantage, all you needed to do was contain the IS-2 and capture the rest of the map. Specifically, you should have immediately built a Panther.
As you found out later, with the Panther and your Panzerschrecks, you would have won an engagement, and your HMGs would have countered any Soviet infantry that try to engage you. You should also have stolen one or two of the abandoned AT guns using your Pioneers (there were two with full health right outside of your base on the right) -- these along with your Panther would have easily beat the IS-2. Because you had the MG-42s, you really didn't need more Panzergrenadiers. Engaging the IS-2 like you did, using only Panzergrenadiers, results in heavy manpower drain through their expensive reinforcement cost.
In that game I often thought about possibilities how I can beat that. I was thinking about a PAK43. But there where more that 1 Pak, that could use their arty-ability to kill it. I was thinking about an arty to counter that russian paks but I never had 600 manpower. I need that manpower to hold my points, to be still in this game. How can I beat that combo? How can I win such a game?
As I detailed above, the best way to beat a strategy like this is to not allow it to reach the game late intact by forcing your opponent to deviate into building SU-85s. The next best way is to counter the AT guns using your chosen variety of fire support unit and a combined arms force of Grenadiers, AT guns, and tanks to counter the KV-8s and IS-2s, along with a couple of MG-42s to counter any Soviet infantry that gets in the way. There's no simple solution when both you and your opponent have combined arms forces, it's a matter of who has the better unit mix and controls his units better during fights. I agree with you, I don't think a Howitzer would have been a good option that game, and because there were so many unmanned Soviet AT guns on the map there was no need to build a Pak-43 or even AT guns of your own during the late game.
Good job pulling out a win at the end!
By the way, your opponent surrendered at the end because you destroyed all of his tanks while keeping yours alive, and he didn't have the fuel to replace them. I'm not sure if you watched the replay yourself, but I always find it useful to do so when I'm wondering what I could have done to beat a certain strategy. While you're playing it can look like you don't have any options, but in watching the replay you begin to see all of the weaknesses in your opponent's strategy and decisions.