Mobility and general advice please.

Hi there, just a brief background of illnesses etc, asthma since a child, heart attack at 28 from a birth defect, heart disease, nerve damage in thigh (which has now over the years reached an unbearable point) and knee broken multiple times which needs multiple surgeries (as I am self employed impossible to do), and lastly and the hardest one, first time probably openly admitting it, serious mental health issues, I was in foster care, abused, then ran away and was homeless from 15 to 19 when I met my now wife, this combined with my heart attack has seemingly messed me up a bit and now feeling like I am grinding to a halt.

Father of three children, self employed window cleaner with my wife.

Sorry for the long winded intro, thought it best if people know my position.

I have been struggling for maybe or 5 years physically with my leg, our business that was thriving is slowly grinding to a halt as while I can drive OK (in discomfort but doable) I can only really manage the fronts of a house (we do this with poles, I can literally walk 2 meters to the house from the van to clean and walk back) or two before having to stop due to pain, in the end my wife ends up doing 90% of the work which two of us used to do.

Essentially we need help, I would happily have my leg amputated and have toyed with doing it myself if it meant taking this pain away, I think I would do better honestly. 

The problem though is with the mobility questions and distance I can walk. The way things work with me is kind of like first thing in the morning my pain is at a 3 and I can operate and walk OK, I walk with a limp and every step is pain but I can function decently, so if you asked me to walk on a good day first thing I could probably walk quite a long way before my leg goes (this is how describe it, the pain ramps up to unbearable levels really quickly and I will say to my wife "my legs gone" and she knows) but once its gone that's it, walking any steps at all is just unbearable, I've ended up lay in the street before now. 

Everything we do revolves around my leg now, if we go shopping I sit in the car, we went on holiday, we have a caravan, I was either sat in the car watching the children play on the beach or sat in the caravan.

So the problem I have is how do I answer the question? I work two days a week and do some work in stops and starts then for the rest of the week I'm crippled.

Does the fact that realistically on a good day I could probably go for a reasonable walk mean it doesn't apply to me? if that's the case I don't know what to do, I am as much as I hate to admit it and fight tooth and nail for it not to be so, but I have become a burden on my wife and I don't know what we are going to do for money.

Any help or advice greatly appreciated, not sure how much longer I can work for.