55 Gal FOWLR - seeking criticism

[Aquattro]

If possible, I'd get a bigger sump. More (cheaper) skimmers available for in-sump use.
As for drains, yes, 1 would be fine, I use 2 x 1" on my 180 and I'm happy with that, so half that on almost 1/4 of the tank would be fine.
I'd look for a used euroreef or other needle wheel skimmer, they're for sale here all the time.