Here's the answers to your questions
1. Yes, your 10 gallon would work. Instead of using acrylic baffles, use glass. You can have them made at any local glass shop for cheap. Then silicon them in. Make sure to use silicon that is aquarium friendly.
2. I think the 10 would work with 54. But if could get ahold of larger tank for the sump, the better. Now would be the time to do it rather than later. You could pick up a tankonly a pet shop for about 30.00. Maybe free in the classifieds. I'm currently set-up a 50 gallon reef with a 20 gallon sump.
3.yes, the sump would take the place of your canister.
4. the filteration comes for the sand, rock and chaeto, crabs, snails etc. That is pump in the sump/refugium.
5. Once, you have design in mind and have the items to build the sump. It takes about 2 hours to build and 24 hours to cure the silicon. What take the time IMO is the plumbing part of the overflows and the return pump.
here's my personal email, I can send you photo of my set up. And give you personal recommendations.
richardlewis68@msn.com
Keep the questions coming.