Your credit card debt is the first priority to knock out. Retain an emergency fund, especially with a house. Then invest.
What are your prospects for increasing your income? $20K seems very low.
Have you given your X an eviction notice for August? With a cushy deal like that, what's the incentive for her to ever move out? What if she doesn't have a job after graduation? Or she says it's not enough to live on? You don't want to wait to start eviction proceedings after August, because (depending on the laws where you live) she could continue to live there for months after you start proceedings. Start them now, so you know she has plenty of time to make the move out happen in August. Since her parents are familiar with eviction proceedings, no doubt they know what they can get away with. I'm sorry you're having to deal with this, but it could get worse. Hopefully she won't trash the house.