The tang's ich was probobally partially contributed by the small size of the first tank. A 29 is way to small for a tang.
Dwarf angels should be kept 1 to a tank. Mixing could cause agression issues. Specificly flame angels can be very hearty as long as you get a healthy fish to begin with. Way to many flame angels are still caught using cianide and the mortality rate is very high with that kind of capture. If you find a flame thats eating well at the LFS
and is freely swimming around infront of everyone thats a good sign. If you find one sulking behind decorations and not eating well then stay away.
Some species of butterfly fish are not hearty at all yet others will fair ok in a larger tank. A 55 gal
tank still may be to small for a butterfly.
Unless you plan on using the canister as a water movement device there is really no need for it as a filter since you will have 90-100lbs of live rock an a 3" sand bed doing the filtration for you. Add to the list a good quality skimmer and a few powerheads and you have yourself a FOWLR