1. When Producer says he’s entering 灯織, he’s referring to Hiori, not the light. The kanji 灯 in her name just happens to mean a light or lamp.
2. Mano’s saying キツい, which means it will be tight, intense, and hard to endure at first. There are quite a few meanings bound up in the word キツい, which has quite a few related definitions. However, the gist is that P-san’s so big, it’s going to be rough at first. (I think the original translator may have misread this as きもちい?)
I’ll go ahead and tweak the translation, but I’ll leave the check translation tag so someone can proofread my changes.
Updated
Umm...It'll be fine.
It might hurt at first, but then it will start feeling good.Well then, I'm going to enter Hiori.P-san's big, so it’ll be tough at first.