Hi! Yes, I used vertex snapping for the sprites in my game! It's not always successful, especially in the larger spaces when the camera moves to follow the player, but overall I think it's ok!
I've also made sure that the sprite sizes are consistent even for particles! As you say, I think it's these little details that are crucial to good rendering!
As for the problem you describe with the aiming direction, you're not the first to talk to me about this, and personally, I always have a bit of trouble understanding what's wrong with it.
It's not easy for me to imagine the solution you describe in play.
Can you think of any games that would have the virtual pointer you're describing? It would really help me understand what could be improved in my game!
Thanks for your comment!