Awww, Wolfie! I'm sorry to hear he didn't make it :( I was hoping he'd be okay.
Congrats on the new guy, though. . . CUTE!
A word about the QT. . . the 3 month time frame is set so long because of the chytrid fungus. If all of your frogs are together already, then keeping them in QT longer than the standard few weeks isn't going to do any good, as the fungus only affects frogs :) I agree with the PP - the 5.5 is a bit on the smaller side for what you want to do.
My frog refuses to eat sinking pellets, too. Utterly and completely refuses to recognize them as food. I also feed a variety of wet-frozen (and defrosted!) bloodworm, brine, mysis, krill, frozen tilapia - he'll seemingly eat anything else, as long as it's not a pellet! Some have great luck on pellets, but they never worked for mine.
I don't know if you have them living together already, but I just wanted to add that while some people have great luck keeping Betta with ADF, others have had nothing but trouble. Be sure to keep a close eye out for possible aggression, and to make sure that your frog(s) are getting their fair share of food, and the betta isn't getting too much.
You'll have to post a pic of your setup when you get it all up and running :)