Him facing Vader was my own go to after all those trailers to be honest.. space martial arts and Vader .. I was sure this would be the climax.
Now thinking more practical even if we give him some lesser force powers like you suggested is that we underestimate Vader in all of this, that dude was special and very powerful in fact so powerful that he is still top ranked even after being reduced to a head with a torso, if that dude was complete he would have killed the Emperor a long time ago.
So powers of the level of top ranked characters like Vader, Palp, Snoke, Luke, Rey, Kylo, Yoda, Mace you kinda have to have them innate on an already high level, you can't train to be in that league you either have it or don't. Yes you can expand on them with age and more practice and research but you don't go from maybe I have some force 'luck' and can move a rock to then fighting someones of Vader's pedigree.
If someone doesn't have the force (even in a lower capacity) they stand no chance vs high level users they will just choke o fry you from the get go.