. , we have income less PITI, less lawn care on the duplexes, less routine maintenance (5%), less turnover costs (7%), and misc items like education (1%).  

Long term major repair reserves should be at least 10% so there you have 50%.Now if your rent is actually $2000/month, insurance, routine maintenance etc will not be 10% but probably less.

It is my understanding even if it were covered under the disability laws that you would not be responsible for providing it, just that you allow the modification if it is not burdensome and that they must return it to normal when no longer needed.  

I do affordable housing for disabled vets in big cities around major VA hospitals and it's like night and day when I look around here (Atlanta is on our list, hopefully before the end of the year btw)

During the gap between the eviction and the Sheriff showing up, I got a call from the tenants girlfriend saying that the tenant had just won a large disability settlement and if I didn't have him evicted and just waited another month I'd get all my back rent and all costs, etc., and if I would consider this, she'd get the lawyer to call me.

Then they found out our income will go down some in three years as my wifes disability from her work will expire, not social security.

I'd do my best to stoke up a bidding war and let him tell me what concessions his side is prepared to make.From what I'm reading it sounds like you were in a routine negotiation and you seem to have taken offense that the other side wanted a better deal.  

But we are routinely generating $30k to $50k profits per house.

Reality is more painful, with vacancies, new roofs and routine maintenance all "eating away at the profits".

If you can repair it to routinely work correctly then no you don't need to replace the door.