I’m far from being a relationship psychologist... what I say, is merely my opinion and my own version of logic
First, I figure your guy would be more than happy to start teaching you at least some basic ASL, so that you two can talk when alone (if there’s nobody else to interepret, and faster than writing notes all the time!)
Secondly, try several books. Some may be easier to study than others. There’s also video tapes. Might be a bit of a hassle, but try libraries in a 50 mile radius, rather than just your own city one.
Also, find out if there’s community centers or schools that are teaching it. I didn’t know mine offered, until the interpretor at church told me (and only because I said I was interested, otherwise she wouldn’t have known!). That one might be a bit difficult, because of conflicting with your schedule, or classes already started, or something.
And, be patient. Not just with him, but yourself. I wanna know everything at once, and gotta keep telling myself to just hurry up and wait! (That, and my teacher said you can’t learn everything in one night, too...I kept asking for signs for all sorts of stuff, before class even started last time LOL)
There's my two cents