You initially said that you made a profit by buying your council house at a discount, then selling later. It would seem obvious that if it was sold for the market value of the area you should be able to buy something else in the same area. Or at least put down a very large deposit on somewhere new (and get a very small mortgage even on benefits - a relative has done this after inheriting). It seems an utterly peculiar situation that the council only gave you 26k if that wasn't the price, or close to it, of nearby equivalent properties.
You also said you couldn't buy in your 20s, as if that was the end of it. I was simply pointing out there's not a time limit like that for buying somewhere. Especially as it sounds like property prices were very cheap in your area, and you were previously working. You mention wages but no dates - presumably you were not working for less than minimum wage? So your full time job of 12k, whilst that sounds low today, would have been enough to live on reasonably.
You SHOULD be grateful to have a council house (and a house not flat!) and you have said you are, so no problem there. You recognise how helpful a thing it is.
I don't know why you're so upset about it being pointed out you're not the poorest of the poor. You say that's because of disability benefits, yet you were working before that so surely either better off then or at least not desperately poor (ie. on basic UC). You certainly wouldn't have been scraping together rent not covered by UC, as social rents are always covered in full.
I was on disability benefits before, for a long time and for hellish reasons. My capacity to work is still affected (and always will be) and I'm currently on a significantly lower income than your Mum's pension and paying half of it in (private) rent, so yes it is a bit galling that someone who's had more opportunities to work in the past and the opportunity of council property talks as if they are so hard done by.
And the teacher thing - if your Mum was working full time as a teacher when you were small, she MUST have been better off than people in lower paid jobs, or out of work for whatever reason. She was not the poorest of the poor either, working in a professional job!
I will add that about 10 years ago I was on the equivalent of 20k a year, like you mention your Mum was just before retirement. Frankly, it felt like a fortune to me. (I say "equivalent" as it was less than that but was disability benefits, so I worked out I'd need to be earning 20k to be on the same amount. I worked it out because I was trying so hard to better my situation and come off benefits against the odds).
Not sure how you can be so sure your benefits will stop - if you are still disabled you MUST appeal.