It turns out, Merlin really was constipated, I'd overfed him (worst betta mom ever T-T). The epsom salt treatment helped him yesterday, and he most have pooped this out last night:
Besides it's massive size, I don't see anything else wrong with it. Merlin must have taken my words to heart last night of "I want to see your poo" since it's in plain sight, as you can see.
Merlin seems to be feeling much better this morning, he has even been flaring at his reflection in the 5.5 gallon since he has it all to himself at the moment. Still going to do one more Epsom Salt treatment with him tonight (unless that's wrong...?) and then I will just go back to heat treatment since it doesn't seem like he has internal parasites. Dragoon will move back in with him then either the following day, or the day after that.
Dragoon is still doing fine, swimming happily around. HE at least liked the Omega One pellets, then again, I think he'd eat anything! He hasn't been clamped up at all, swimming normally, and I'm hoping he stays that way!
I do have a couple questions with the pellets?
-Since Merlin is still a bit bloated, how much should I feed him until he seems back to normal?
-How many pellets should I feed both my boys (assuming they're both healthy) for one meal time? I really don't want to feed them two-three times a day since they've gotten used to only being fed once a day.
Thank you all once again for your help! I would surely be lost and even more terrified for my boys without all of you!