His account is "broken?" Could that mean it is frozen because of a dispute or claim against him? Or could it be a ruse to get you to not pay to the actual account holder who has no idea anything was being listed under his/her account. I said "listed" not "sold" because you're not likely to ever receive the item.
Actually, it could be that someone's account has been hijacked. And the hijackers haven't thought the whole thing through - like how they can be tracked down through their PayPal account. Unless, of course, they managed to figure out how to have something billed and sent to a completely different address without anybody ever finding out. But crooks aren't usually that bright.
This does NOT sound good! Asking you to use a PayPal account "outside of eBay" doesn't make sense. For one thing, you wouldn't be protected in any way should the item not arrive or arrive broken or any other problem and the seller does nothing to rectify the matter.
Give him YOUR PayPal account? WTHeck does THAT mean? Did he expect you to give him your password and email connected to PayPal? I don't like to be harsh on anybody, but this guy is either nuts, very dumb or a crook. With all other things considered, I'm leaning towards crook.
I hope you haven't sent any money yet and I hope you saved his emails. I'd send copies of his emails to eBay along with an explanation like the one you wrote here.
Good Luck!
Deborah