I want to start off by telling you that you're right. I don't deserve your son. I could spend the rest of my life (and maybe a couple of lives beyond that) solely working on becoming a better person, and I still wouldn't deserve him. You don't have to tell me that. Nobody will ever have to tell me. I already know it to be true.
With that said, and I genuinely mean no disrespect, you don't deserve him either.
Your son is the most incredible person that I have ever met. He has the kind of heart that draws people to him. He will accept any and everyone into his life, regardless of how flawed a human being that they are. He gives so selflessly of himself and of his time just to be sure that all of the people around him are happy. He never asks for anything in return. Even as I sit here writing this, I realize how incredulous you probably are about that, but it's the truth. He has the best sense of humor. He can get you laughing even when the rest of the world feels like it's dark and closing in all around you. And he's thoughtful even when it isn't expected, even when he doesn't have to be, like he just doesn't want you to ever forget that you were on his mind. He is the sort of man that can make even the world's worst cynic believe that happily ever after is a thing that exists. He will forgive you of things that should be unforgivable, and he will do everything that he can to help you forget that you made even the worst of mistakes when everyone else in the world only wants to remind you of it.
You may wonder why I'm telling you all of this. He's your son, after all, and these are things that you should know about him. That's the thing, though: You don't. You don't know this unbelievable man that your son has grown up to become. I don't know what you see when you look at him, but I know that it's nothing like what I see. It's nothing like what anyone would see if they just took the time to look. I might not be very smart, and I may not know a lot of things, but I am absolutely certain that you will regret it if you don't open your eyes. You're missing out. You're losing so much goodness not knowing who Morde really is.
Morde loves you. I know that it might be impossible to believe, but he does. You're his father, and some part of him is always going to need you to look at him, not through him. I wish you would. I hope you can. I really think you'll be surprised to see how he's grown in all the time you didn't bother to see him. You know where he'll be when you're ready.