I think our other valuable contributors have covered a lot of the bases for you with solid commentary/advice.
I guess the lesson to have learned is that the term 'poly' is really a pretty broad umbrella. Nothing that you wrote (unless I missed something) falls outside the framework of poly. His 'poly-ness' solely relates to his ability to be in a loving, meaningful relationship with you and someone else(s).
As for the discovered sexual tastes, that's just more complex. Although sex is a big part of most relationships, it's also a topic of it's own - not to be confused with 'poly'.
Our sexuality - especially in this society - is VERY complex. We can live and love with people for YEARS and still discover (or not) new sides of someone's sexuality. And it's a moving target. Our sexuality changes over time with our learning, exposure and experience.
So unless you 'discover' something that you find scary or truly offensive, I wouldn't confuse my apples and oranges. It's very common for partners tastes to vary and there's no requirement that both be identical. In fact part of the attraction of poly is to eliminate that conflict !
Join in what you enjoy - opt out of what you don't. As long as it's all safe and consensual it's all good.