The Marder should probably not shoot at the KV turret (even the back of it), unless it's stock. The upgraded turret has 110 mm armour all the way round. Best option for a Marder not shooting "gold", is to aim for the machine gun port in the front or the drivers hatch.
Angled KV1 = machine gun port.

We are discussing the Marder 38T right? the one before the Stug. Not the tier 3 Marder II? Well... I see they have more or less the same guns so nvm.
KV-1 is a tier 5 tank - and your team's tier 5 tanks should deal with the KV-1. E.g. the American small but mighty T49 - will eat KV-1 for breakfast.