I agree with the "move on posts" Nothing I can add, You are not dealing with a "child" but a grown Man who has shown his real self..
From only the info in your post, it is not your "doing" You are the biological Father but is there really any other connection?
A year or two ago you told us about the $10k and everything else. Back then you said you were done with your son and his disrespect for you over boarding his dogs while he moved to San Francisco. You said your son could kiss your ass. You were telling him to have a good life and that's that. Now you're companining that you haven't heard from him in 6 months and birthday cards are being retuned?
My advice is that repeatedly lashing out at your family on the Internet isn't the answer.
Forget about the $10k and all the other BS in the past. Clinging to all that resentment feeds bitterness and makes any hope for reconciliation impossible. Even if you don't want any reconciliation with your family, unburden yourself of the past anyway. And if your son blames you for everything bad in his life he's clinging to a lot of resentment himself. Get rid of the resentment or your past will destroy your future. That's just a reality of life.
My wife and I are the only two members left in our families, that we care about. As a gesture, I said to give her brother her old (13 years) Toyota in January, when she bought a brand new Toyota. He was extremely grateful, because he is in sad shape financially, and medically. I guess he is retired, and on SS. He is basically on welfare, and has subsidized rent for his apartment, not being able to work for many years.
Other than that, we do not have much contact with him or his 3 deadbeat sons......well 2 of them anyway. We have put them in our will, since we have no kids, or anybody else. It's going to be a fine payday for them, when we both die! It's better than leaving it to the state......but not much. Donna wanted to do something for them, too. Bob