You are right. You do deserve to have your needs met too. But you are not going to get them met with this man. The “affair” in your marriage has been substance abuse for years. He can leave you because he is more committed to his addictions than he is to you.
Although you have worked hard to take care of your own issues, you can’t make a relationship by yourself. Staying with him means you would have to tolerate always coming in second to alcohol and pot. You deserve better.
Unrequited love is very, very painful. Being lonely and sad within what is supposed to be a loving marriage is a hard way to live. Unless your husband is willing to make changes, you are signing on for more of the same. For that reason, I do suggest you at least see a lawyer to find out what your rights are after so many years of marriage.
Do consider whether being single is worse than putting up with your husband’s treatment of you for the rest of your life. Chances are that being free of the constant stress and disappointment will open up new possibilities for you — including the possibility that you will find someone who will love you and cherish you and put you first.
Please consider finding a therapist who can provide you with some needed support and perhaps some guidance during this difficult time.
I wish you well.