My father never comes through. When will I stop believing his promises?

Time for a re-set. It sounds like you want to believe him and repeatedly choose to in spite of past events.In some ways you are an enabler. You let him lie and he knows it. Time to stop, if you really want things to change.You may need to get a therapist to learn how, but you need to base beliefs on actions, not what he says.When you can, that changes the dynamic.