I have done a lot of flying in Coach (see my name) and have flown many transoceanic trips over the years. (I am 5'4", so legroom is not a big deal for me.) I also have a disabled husband who needs to walk with either a cane or a walker, so I know something about AA travel for the disabled.

The OP cites all kinds of medical conditions which he uses to justify the need to somehow dissuade the passenger in front of him from fully reclining. It is my opinion, based on experience, that the OP should have made his disability known to the airline before booking the flight. We have done that when my husband travels with me.

We ask the airline to put a note as to his disability in the PNR, then when we get to the departure gate, we ask for early boarding so he can stow his walker in the closet. They are always happy to comply with our request and treat him with courtesy and dignity. Talk about "early" boarding - sometimes we are the very first passengers to enter the Coach cabin!

Usually the bulkhead seats are blocked in advance seat assignment seat maps. I believe, but am not positive, those seats are assigned to disabled people and others in need, such as families with young children. The OP could have called in advance, disclosed his disability, and might have been assigned one of the bulkhead seats.

There is an important caveat: Exit row seats cannot be assigned to disabled people. If you self-identify as disabled, you may not sit in an exit row.

In my opinion, the OP handled his situation incorrectly. He should have requested disabled seating in advance. If nothing was available, then in order to save his life, he should have booked a later flight. It stretches my imagination to think that a person with a potentially life-threatening disability would voluntarily put himself in a potentially bad situation, just to get home a few hours earlier.