The KV pistol ports used a plug on a chain. I don't understand what you mean by fabricating the two rings on the turret? Your model looks like it is an HL with the supplemental armor removed from the turret. The area you have circled looks mostly normal to me for that early welded turret.

In rarer cases the Soviets apparently actually did use camo paint schemes. I don't know much about the Soviet camo, I have to research it more. For solid colors, in addition to the standard green, they used an ochre (yellow-brown-green) color too.

That walkaround link killick posted is of a later model cast turret KV-1.