I am going to say this with as much grace as I can.
I understand what your friend told you. However, thinking like this will keep you stuck.
You are not abandoning him if you are making your life for you. You are not abandoning him if you are happy.
As long as you are breathing, I doubt that you will ever totally abandon him.
However, the most that you can do, really and truly the most that you can do, is move forward for yourself. Take a step everyday. Even if it is a teeny tiny one.
You can let him know you are there. You can make your home a safe environment in case maybe he decides to come around. You can work on yourself and make yourself and even greater TF than you are right now.
But you can’t worry about abandoning him. He has to walk his path. He has begun this journey and he needs to finish it.
If and when the time comes for you to be done, you will know. If you continue as you are going now, you will also know that you have done everything you could to stand. I’m glad you recognize that when you feel that way right now, it is just out of frustration.
You are doing good. Very good.
"Acceptance doesn't mean resignation. It means understanding that something is what it is and there's got to be a way through it."--Michael J. Fox