exterior wall vent

Hi all! I am planning on installing a bathroom in my basement, I live in Maine (IPC code, I think). I have easy access to the main stack to the septic system but venting the drains (and up flush toilet) is going to be difficult. After hours of research I am totally lost on when wet venting is...

I am remodeling my shower, which leaked over the course of 20 years and left me with rotten floors and joists (fun!). Anyway, the missus asked me if we could change the existing niche to be an "infinity niche" (wall to wall niche). I noticed that the niche wall, which is along exterior wall, was...