Sure, glue the sucker down, if he's mad, he'll detach though, so make sure he is happy before you glue him.
The white center is his open mouth. It will be fine, they all do this when stressed.
Zoos don't feed I don't think. You can feed the shroom cyclopeeze, I have some ricordia which will eat silverside pieces. They are hard to feed IME, so maybe just dose the tank with some cyclopeeze at times (turn off your skimmer of course).