Thanks!

It's possible that's what caused it initially, to be honest. Between 2021-2022, I was dealing with some pink mold on the bathroom ceiling due to condensation. I ended up replacing the exhaust fan hose, upgrading from a 50cfm motor to a 70cfm one, piling many layers of insulation in the attic above the bathroom and around the fan housing and repainting the ceiling with semi-gloss mold-killing/mold-resistant paint.

Needless to say, all of that helped the previous issue, haha. On a freezing cold day, I can feel a slight temperature change if my hand is literally right on the fan vent, but again, it's not what I'd classify as a draft.

The exhaust isn't directly above the shower, it's more in the center of the bathroom. That said, there isn't really a draft coming from it. If you stick your hand right over it, you can sometimes feel cooler air from the attic above, but not a draft.

I'm as sure as I can be without ripping it all down, haha. It's sealed up tight and I check often to ensure the silicone hasn't cracked. There are no odors or soft spots that would lead me to believe there's water/mildew/mold, and it's been like this for a few years so I have to imagine it's dry back there -- at least until something happens that suggests it's not.

It's attached well in many places, including at the top by the drywall. It's a few spots in the middle that are pulling away. I wouldn't necessarily call it "falling forward" -- it's more like there are some air bubbles in the middle.

I was kidding, haha. It looks terrible right now but it's just aesthetic -- I'd rather have it ugly and keep water out than have a barely visible crack that lets water in. There's a hole in the laminate floor in the basement from when I dropped a 500 lbs. barbell doing squats, so there are several things in my home that buyers may question but I'm not going to advertise them. We can deal with that stuff if they ask about it.

I ended up using Devcon epoxy/fiberglass repair and it came out awful! Gonna try wet sanding around the sides when it dries.

I forgot I had a pack of Devcon epoxy bathtub repair, so I’m gonna try my luck with that. I already sanded a little bit past the track, so I should just need to spread the epoxy, lay the fiberglass cloth over that, and then spread more epoxy over that.

EDIT: I just finished and it looks awful. I'll maybe try tidying it up around the edges with some smooth grit sandpaper when it's dry, but we're probably moving within the next five years or so, so worst case scenario, I knocked a couple grand off the asking price of my house, haha.

Mine is a fiberglass three-piece shower surround and the crack is basically in the middle of the back panel. It’s SO thin but there’s a clear separation where water could get in, so I just want to keep it out. I have touch-up paint specifically for the tub, but I don’t think that would fill the crack. I was thinking either silicone, or maybe even a thin layer of epoxy followed by the touch-up paint.