Unfortunately, I can't help much with a vitamin to help.
However, I can give you some personal experience. I have had my right ear drum rupture once and my left ear drum rupture twice. (all from an infection). I was younger when this happened. (about 12 and then 16). I didn't do anything above and beyond, really, to help them heal. I kept water from going in them for the first few weeks. (meaning, I was very careful during showers and I stayed away from pools). But, mine healed naturally. I do have some scar tissue (I don't heal well) and some minor hear loss in both ears, but that is to be expected.
I do however remember some drops that the dr prescribed me to help with the discomfort and irritation. (I'm fairly sure they were either 'numbing' or 'soothing') But, you would have to ask his doctor about those.
I hope he heals well and is feeling better shortly. Please keep us posted.