LOL WELCOME home

Yes you met our claw hater Wit

All hermits are questionable IMO ( and evil in his)
The damsel needs to go. If it were a 75-90 I would say one is OK but your tank is to small for any damsel IMO.
The slug is probably a Stomatella. Here is a nice pic from Gumhead a member here.
Dave where is that close up from the other site?
The small brown globs are probably just worm poop

HIH
S
^EDIT^
If it has no shell and is totally soft it’s probably a nudibranch(SP?) of some type and there are many out there. Most are not safe to a reef IMO
S