Man, I really enjoyed this. It's a niche I've always hoped to see explored, and there's a ton of ways it could get expanded upon.
I'll start with a bug report: I had an issue at the restaurant where the door didn't reset after a loss. The door was "open," but the button did nothing, and I think it was behaving as if the door was perma-closed? No one approached, though the purple thing was still able to get me. Might've affected the light too, but I could still use the button to turn it back off. Re-opening the game fixed it.
Next, a couple small criticisms: First, it might be worth tweaking the straps of Rex's tank top outfits. The one with the plain black tank and black shorts looks really good, but the other two tank tops look kinda awkward, like the straps stop at his shoulders instead of actually going over them.
Second, XP gain slows down... a lot. By level 10 you're basically grinding the exercise minigame over and over because it feels like the only way to make progress, and it gets hard to tell what's actually earning XP and what isn't. Maybe leveling up could add options or expand various activities for more xp? Like more plants, levels for the shooter(is that endless, by the way? I couldn't tell), etc. Keep activities feeling more relevant and therefore less repetitive, basically. That said, this is the sort of thing that's entirely understandable for a game that's not complete; I mention it mostly because I couldn't tell for sure if I was missing a better way to get xp or not.
For outright suggestions, I have a few. First, it'd be fun to be able to steal his hoodie and leave him in an undershirt or something until you reset his outfit. Feels like that'd fit right in.
Second, a sleep/nap mechanic, or just the option to do so. Bedroom, living room, camping... cuddly sleepytimes would be fun.
Third, because my horny side also has thoughts, an edging system could be really fun, or a system where Rex's lust ranks up instead of maxing out, getting him needier and needier.
I haven't exhausted the game yet, but like I said there's a lot of potential for it to do all sorts of things. I really look forward to see how it gets fleshed out.