Be careful... We are talking about the Daedric Prince of forbidden knowledge & fate. Nothing is impossible to this bastard. If there is a way, Hermaeus-Mora will know it. It's up to him if he wants to share that knowlegde or not. I have no doubt that he is the strongest Daedric Prince. In all likelyhood, he was the one who probably leaked the knowledge to curse Jyggalag in the first place.
Sorry to break it too you but the strongest of the Daedra (if any at all, not including Jyggalag of course) would most likely be Molag Bal as stated earlier. Most of the lore about him shows him as the most powerful (in one book, the one with the bow of the hunt, it states that all the Daedra "quickly agree with (Molag's) view, as they always did" and him being the most fearsome of the Daedra) and he is the lord of domination after all. But this is a little off-topic.
EDIT: And if not Bal then at least Dagon. It took Akatosh to defeat him. I would say HM is powerful but he's definitely not on top.
Ugh my head hurts. I don't think a daedric prince would even be able to "make" a dragonborn. Since the whole point is that they're essentially men (or women) born with the soul of a dragon. Since the soul is a persons essence, its probably the only thing HM couldn't figure a way to alter. That's not to say he might not be able to ,say, kill a dragon, take its soul, and place it in a mortal body, thus creating a dragonborn, but then he'd have to teach an entirely new entity everything about the thu'um and the world in general. Just to make a dragonborn. Seems like something a daedra would do for entertainment but it would effectively destroy the mortals mind and create a new person. So it wouldn't work in this instance.
I sincerely hope HM did not "make" a Dragonborn....