Update: Mac got 4 full droppers worth in a shot glass and then I poured in mealworms and let him eat his fill. He polished off the 4mL of B-complex!
He's doing great for day 1 with the proper dose. He doesn't seem to be seizing anymore when he tries to stand, and can actually balance a little by himself!
He's still on his hocks (idk if that's what the part of the leg is called), but if i hold his leg in a way the puts him on his feet, he can balance by himself for a short time.
Thank you to everyone for all of your help. We aren't out of the woods yet, but he's improving steadily and I will keep you all updated!!