By water parameters, I mean pH, GH, ammonia, nitrites, and nitrates, and maybe even temperature just for the sake of being thorough. If you've checked that they're all ok, I would assume that's not the issue and it's the stress of moving. Is he being bullied by other fish? If he didn't take the bloodworms you offered, that's pretty weird. Never met a betta who wouldn't fight scale and fin for those things. Next time you feed something high quality like bloodworms, take note of how the fish interact. Are they scaring him off? I agree that Mollys and Bettas don't go together all that great, seems to always be some power dynamic. Little jerks.
You can upload the video on youtube first and then share it (an annoying process, I know, but it works). If this is too daunting, please describe how he's swimming. In a tired lethargic way? Is he struggling to stay upright? Does he seem to be floating upwards against his will? Or sinking?
