You've asked for help making a decision. No one can give you that, least of all strangers. It's a very personal decision that only you have the right to make. If anyone can help you, it's got to be a trained counsellor as so many have said.
Perhaps you're looking for opinions that might help you make sense of the part of having an abortion that seems to feel 'wrong'. Or validation that you do 'need' an abortion. You've had all that.
But if I were in your shoes, I'd want sympathy and honest reactions, no matter how unwelcome. So that's what I'm going to offer. I'm genuinely gutted for you - how awful to be landed in this situation again, knowing you can't face the thought of another child. I completely understand that. If I became pregnant again, I would probably face a lifetime of pain and severe disability. I honestly don't know what I'd do. I also can't imagine bringing up my toddler alone. I know I somehow could if I had to but anything harder is impossible to imagine. I have deep respect for every lone parent. To my mind, they're all heroes.
But here, right now, from where I'm standing, I have to acknowledge a deep personal conviction that abortion is morally wrong. It's a life, not just a few cells anymore than we're just bigger groups of cells.
Do what you have to do/want to do, I've no desire to judge you and wouldn't think or feel differently about a friend if they went ahead with it. But don't ignore that conscience within yourself and don't allow anyone to blunt your awareness of it. There are a million good reasons to do many things that are morally questionable. We learn to live with the grey areas in life. But it's never simple and it's always sad. Make your peace with that in both scenarios.
One other point. You've said you can't do another pregnancy or do another baby. I understand that. For the purposes of fair consideration, are there ways it could be made more of an option? I ask because my life as a mother so far looks utterly impossible on paper. I couldn't lift my child at all during the first year, our earnings shrank to zero, and we travelled weekly to another country, complete with baby, for medical treatment. It was a different problem, but it was significant at the time. I coped by planning life like a military operation and ruthlessly going after the choices that would make our situation work. It still sucks at times - many times - but I'm coping despite the difficulties. Without diminishing the awfulness you're going through, there's no doubt in my mind that that could also be you, if you wanted it to be.
Deepest sympathy and prayers. Stay strong.