If he got in there, he can get out. But in my experience, any time a BTA has gone to the back of the tank and not come out, it was because I had not done a thorough-enough job of light-acclimating him and he was trying to hide from the light. I wouldn't bother trying to move him until the issues that caused him to move have been addressed, otherwise he'll just move again. My guess is the light is too intense.
I've touched mine a few times and while the tentacles did stick to my skin, there was no pain, no reaction whatsoever. You do have to remove the tentacles carefully, they can get damaged if removed too fast. I've gently pulled at their foot with my fingernail to get them to dislodge, no issues.
