The only person who can evict is the landlord – not you. If he’s not supposed to be there to begin with, is causing various problems, is making threats, and isn’t paying rent, he should be evicted – but the landlord is the only one who can do it. There is no way around this.
You can't stand him, he is an unemployed felon, yet you're trying to put him on the lease?

That makes no sense whatsoever.
The only way you can get your money back is to sue him. Very foolish for you to buy items on your credit card for him without a written agreement/promissory note for him to pay you back.
His problems with the mother of his child are none of your business.
Clearly you are afraid of this person. You need to grow up, put on your big boy pants, and learn to make better choices about who you allow to live with you and who you choose to let use your credit card/give money to. Or, you can just continue to be afraid and continue to let yourself be used. The choice is yours.