To add to what Mr. Limpid mentioned...
50 hermit crabs is way, WAY too many...they'll compete for food, run out of it and will start on your snails. If you want to keep hermits and snails, your best bet is to go with scarlet reef hermits (Paguristes cadenati). They're the most docile of the hermits and are the least likely to prey on your snails. It's the only hermit we'll keep in our tanks.
As for how many, I wouldn't stock hermits at more than 1 per 10 gals in an established tank, so no more than 10 - 12 for a 110.
Snail-wise, stocking levels depend on WHICH snails you're getting.
I'd go with a mix of Astrea, Trochus, Nerite (the tan ones with black markings), Cerith, and a few Nassarius (the don't eat algae, but will replace hermits).
Stay away from Margarita snails, as they're a temperate water species that won't live long at tropical temps. I'd also hold off on Turbos, as they get large and are clumsy, and are really best for filamentous algae. However, if you can find T. castanea (smaller, orange Caribbean turbos), I'd add a half dozen of them to the mix.
Stock your CUC lightly, then wait to see what does well for you and what your tank requires as it matures, then add accordingly.