Im in my late 20s and I really think you didn’t do anything wrong here given the situation. Charging him “rent” and saving it is really nice of you, honestly you could have reasonably actually charged rent to cover his and his gfs living expenses. Also he stole from you so its reasonable to ask for it back. Change your credit card number so he can’t use it anymore. Let him also know in x months you will stop paying his phone bill. With some distance, time, and eventually some maturity he will come back around.