Compare the Kv8 with the crocodile.
Same damage (10).
less range.
less durability.
you need to swap weapons and the 45mm fails to deal decent damage even against halftraks.
Kv1 needs stats in line with churchill and similar units, definitely some hp/armour but its also really bad making damage against armour and infantry.
Also it needs this for vet 1:
And if it still underperforming (i don't think so) then add this for vet 3:
historically acurated:
https://en.wikipedia.org/wiki/Zinoviy_Kolobanov
KV-8 should simultaneously shoot with gun and flamethrower. And a little to increase flamethrower range