Sacred Haven of Debauchery

Okay, regarding all the indirect questions, it has completely devolved into pointless arguing (sophistry), in my humble opinion. So, let's get to the direct points:

Firstly, you are bound by agreements. In the settings, civilized nations set a ban on full-scale bombardments and only use limited ones. Of course, there are those who don't do this, but we are talking in general, which means we take into account all possible scenarios, including those who only carry out limited bombardments.

Okay, I wasn't bound by any agreements. I forgot about that option; if you're unlucky, it might not be enabled.

Given the extremely slow population decline even with the most aggressive bombardment mode, I don't think nuclear weapons are being used on a massive scale.

I didn't notice any population decline at all; is this mechanic definitely present? And considering the typical time scale in this game (months), this could be explained: well, everyone is crammed into bunkers, so few people die, and rarely. But production is completely halted (which is a good explanation for why, according to Stellaris's mechanics, it's halted; there's no one on the surface).