Blalron, I feel your pain. My dad has a user girlfriend–she hangs out with him right after he gets paid and then disappears after he’s used up all his money on her. He knows it too–but he says he’s lonely. I can understand the feeling, but I wish he would find someone or something else to keep him occupied. Someone or something that doesn’t bleed him dry and leave him with no money.
Just because our parents older than we are, doesn’t mean they know any better. There’s nothing you can do to change him. He’s going to have to figure it out for himself. I don’t think you’re out of line for feeling the way you do, but you’re going to have to live your own life and let your dad learn his own lessons.