Yea, that's sort of why I said pick either the goby or blenny, because of aggression from the blenny. I'm not exactly familiar with that particular blenny, but I did have a LMB that I thought was also 'friendly' till he started biting my clownfish. I guess if you added the blenny last, it might work.
For the CUC, I'm not a big fan (mobile inverts in general). Generally I just keep as many different type of snails as I can find, mexican turbo, asteria, cerith, nassarius, and one conch. With a couple hermits, for my 29gal, I had 10, but would recommend less, just 5 scarletts would be my pick. Absolutely not a fan of true crabs, if I had to pick one, after the tank establishes for a while (9 months) a porcelain crab would be cool. The lettuce slug, aka lettuce nudibranch, usually are fairly hard to keep, any strong flow and they get blow around, into pumps/overflows. The clam is a really bad idea, as those need strong lighting (HO T5's with individual reflectors or halides).