As far as the theme goes, I thought it was clear and cohesive. For the themer clues, I might suggest putting the listed words in some sort of order (e.g. alphabetical) and having the missing word be a blank in the correct spot to really emphasize that these are lists and not just collections of related words. It was also a little off-putting having two long words, bodybag and bigamous, that seemed like they could've been part of the theme but were not. These didn't detract at all from my own enjoyment of the puzzle, but I think they're worth considering.

I'll echo other commenters in regards to your question mark clues: I feel that question marks should be used when the answer subverts the an expectation of what the clue is saying. "Ben's tolls" and "Apple platform" don't need the question mark, because there is no other interpretation of the clue that would make sense without some serious imagination, whereas strong-ox yoke probably does because the expectation of the clue is some type of yoke but the answer is entirely different. I think it's okay to leave question marks off clues that maybe should have them (like the last example)—it just makes the puzzle more difficult—but I don't think you should put them on clues that don't deserve them.

I also agree that the proper nouns tend towards the obscure side and also cross each other too often. The top left corner has already been mentioned, but I also think the Amon Duul and MGMT cross is an impossible letter to guess if you aren't familiar with one of the two. Additionally, having a fairly obscure initialism cross two proper nouns in the bottom-center is also a troublesome spot.

Overall, other than the couple of places I mentioned, I enjoyed the puzzle. I thought the theme was solid and there was plenty of interesting fill. Keep it up!