Can playing blindfold improve playing non-blindfold? If I play blindfolded or don't look at the board and just visualize the board, pieces and position in my head, can this improve my regular style of play (physically looking at a board).  Is there any proof to improving regular play via blindfold play?
I don't think there's any proof (nor do I think you'll find any), but I think playing blindfold definitely helps as regular chess practice. The better you can play blindfold, the more you can visualize the board and calculate ahead, in my opinion.

Better yet, try playing blindfold against someone who's not.