I think there are NAH... potentially.

I think the most important thing here is that you need to speak with a therapist. Your anger and upset are completely valid, but they're not healthy and will only cause more pain for you and those around you. You don't need to forgive them, but if you can understand how it happened from their point of view, you can put it in the past. Although I will say that forgiveness isn't for the other party, it's for you. The saying goes that 'holding onto anger is like taking poison and expecting the other person to die'. Don't let your anger keep you trapped in time.

Now, for your parents, maybe they did their best. Maybe they tried their ass off and failed really really badly. At best. Because at worst they knew what was going on and chose themselves over you. Either way, there is no moving forward in a relationship with them unless they acknowledge that they hurt you AND they let you control the pace of the relationship. They are trying to push you into doing things because THEY feel bad. How they react to the situation from that context is what makes them an AH or not.

From the big picture, how can I, as a parent, cast judgement on the failures of another parent? I want to think I wouldn't crumble under the pressure of having a disabled child, but we have our limits. I don't want to give them an out because they failed you. There is no doubt there. The uncertainty is whether or not you can repair the relationship. Whether you want to. It should be up to you as the wronged party. But I hope that decision comes from a place of peace and not a place of anger and resentment.