If he keeps shabbos and kosher in an orthodox manner (there are variations on people thinking they are keeping kosher according to strict Jewish law, but not really doing it properly (does that even make sense?), but get very upset if you tell them they are not doing it in accordance with Jewish law - Halacha (really I don't care what you do, but I do get annoyed when people say they are keeping halacha and they are not (for whatever reason).. be intellectually honest and call a spade a spade).

But assuming it really does follow halacha, then it is forbidden to marry a non-Jew, it is forbidden to touch a women at all (Jewish of not Jewish), and it is not at all accepted in the community. I would find it very strange, and think there is something 'weird' going on with the person TBH, and at the end of the day, I would suggest it is going to end in tears (as I say to my kids... not about dating - the tears part)

Not sure if it is a theoretical question or not, but you can always call me for a chat or a coffee (a kosher one!)

P.S. Just stating my opinion as what is considered an practising 'ultra-orthodox' Jewess (gotta love that phrase!).