In the photo it looks like it has no bracing? If that is the case, then you seriously need to brace it
Anyway, sump would be best, but with a FOWLR tank you could quite easily get away with not having one. You will need a grunty skimmer, which i'd budget around $400 for.
11kg wouldnt be very much in that tank; in fact, 100kg probably would be minimal in that tank :lol: You dont need heaps, but i'd look at getting around 20-30 to start with
Fishwise, you can get whatever you want 8) Its a decent sized tank, so any of the larger tangs would be fairly happy in it.