You already threw him one bone, you bought out his house like he begged you to do.
Time for this guy to live with the results of his actions.
He has already displayed his attitude towards you and money. Remember the rent issue, the complaints about cost, was he your bestest buddy then?
This guy isnt family. He is a user. He takes advantage. If you give him money he has no right to, he will never learn responsibility and how life works.
Again, he would not have given you one dime if you had sold the house at a loss, in that case he would have been all about "hey, it was your house, you lost money, nothing to do with me". But, since your investment paid off he wants some of the money he has no right to.
Keep business as business. And with the money that you invested, it was business.
dago