No criticism taken. On the contrary, it's appreciated. I am very much an amateur builder and always trying to learn more. For the plumbing venting, I did an interior Oatey Sure Vent. I had heard the issue you mention about fresh air when spray foaming the envelope, but I don't really have an answer. I suppose I was counting on the occasional opening of the doors and windows. But that's a fair point. I'll have to think on how to address that to ensure good air quality.
The TH's are only going to have a countertop double induction top and maybe a countertop multi-mode air fryer for simple meals. They're not intended for elaborate cooking, and frankly, my family doesn't do much of that anyways. So we'll probably just open the windows over the kitchenette if we're not just eating out. Probably not ideal, but I'm trying to keep things simple for now while we see what works and what could use upgrading.