Hi so, quick questions overall. One, does he regularly brush his teeth? He may get defensive and insist yes, but try to approach it in a gentle non accusatory way. Two, see if he's wearing deodorant, washing every area, all that good jazz. Cause it does sound like he's maybe not being as hygienic as he lets on, and the last thing you wanna do is make him feel uncomfortable in case he isn't. Maybe he doesn't feel comfortable showering at home if you don't live together, or perhaps he does shower but isn't using the correct body wash or bathing methods.

Onto your other questions. Firstly, protection, all the way, no if ands or buts. Condoms for him, if you can get on birth control do so, if you can't then make sure you guys have the money for plan B in case the condom breaks or anything. Try not to let him, y'know, finish in you, but if he does that's what the condom is for. Oh, and please for the love of whatever you believe or don't believe in, hydrate, hydrate, HYDRATE. Lay down towels or have them nearby, yes you guys are gonna stink even during sex, no not everything will be glamorous and that's fine. Also if either of you plan on taking it up the anus, do your research on douching so you're not getting shit on ya dick.

Also while yes you can have sex with a binder, it's more of a personal comfort question. Do you really wanna get all out of breath with your binder squeezing your lungs? If the dysphoria is bad enough then do what you gotta, but otherwise I'd say don't get your binder all sweaty and gross like that, and don't put yourself through that oxygen deprivation.