I hope so! I can't say much on the breeding dynamics of the crabs... Haven't had mine long enough. Your filters are definitely fine, just pointing out a couple that I've had success with in small water volumes.
To give you some tips with Great Stuff... Wear gloves! If it gets on your fingers it takes a week or so to come off. I know from experience, haha. It's also a lot easier to put your rocks in the pre-hardened foam and then worry about clean up after the foam has solidified. I used a wire brush to get into the nooks and crannies of my rocks on my paludarium. Also, don't work with the foam immediately after it looks like it's hardened because there will be some pockets inside that are still liquid foam.
Lay out your rockwork/woodwork idea on a flat surface before you put it in the foam. It'll be a lot easier to just transfer them on like pieces of a puzzle rather than figuring out the scape right after you've sprayed the foam down. I tried this before and it's a pain in the patoot. Oh and lay your aquarium on its side so that the surface you're gonna put the rocks in is horizontal. You might want to support the back of the panels with something so that the silicone isn't stressed.
One last thing, which is totally optional, but you may want to wet your rocks before you put them in, just to see how they look when wet. Some grey rocks turn a dark black and some white rocks might look clear. Just sayin'