Definitely take it easy on feeding krill. Long term feeding heavy amount of krill is sketch at best, especially if it's not frozen, but freeze-dried (canned) krill. Plently of better foods to feed, shrimp, clams, scallops, squid, silversides, etc.
If/when you get him, I can almost guarantee you'll need to treat for internal parasites. Treating the water with Prazi Pro and soaking foods in Prazi. Also the disease resistance, or there lack of is pretty big. Even if you treat him in QT, if your display is not 100% free, very high chance of breaking out.
One thing to watch is with the angels, watch they don't nip at the spikes. My white tailed dwarf was terrible with the puffer, and even nipped off his antenna above the eyes.
That should be a clue about the aggression, they are near the bottom. Mine gets bossed around by everyone. Very surreal to watch a 2" Rock Beauty tail whip a 8" Spiny Box puffer that could swallow him whole.
The last thing is body weight, he's going to eat a ton, especially when larger. Typical day's meal for mine is 20 or so large NLS pellets, some nori, 2 whole jumbo shrimp, and 2 silversides. The other days he gets squid, scallops, and some octopus. His body should be flat along the bottom/stomach area. If he looks like an upside down bean, with the stomach pinched in, he needs more food.
Did you see my thread in Aggressives?