Looking at this picture it might be a Vermetid snail. These have been know to irritate corals too. If you have any super glue gel around you can put a small dab over the opening of the shell. This should kill the snail. As far as the hydroid/s go, you might want to smother it with a piece of epoxy. It would be like putting a piece of chewed up bubble gum over them.
I'm having a tough time finding the critters in question. That last post I can almost make out what might be a peanut worm, which I've discovered lately in my tank also, reef safe if so.
Light sensitive, round burrow in a rock, sounds similar.