[Solved] Completely at the end of my tether..

Hi,
I assume that like many Dads out there I am at the end of my tether, My daughter who was 18 in May 2019 completed her A levels this summer and plans to go to University. At the time our relationship breakdown, my ex would not agree to an amicable split - sell the large house we had and buy two in the same area so we could both see our daughter - ended up she had a better lawyer, I had to move out literately penniless and move in with my sister. Within a week the CSA informed me in writing of the payments I had to make and until July 2019 I had not missed a payment. After two years I managed to save enough money to get a mortgage on a house 50 miles away (nearest to my daughter I could afford).I now have a job local to my house earning 55k per year. I told my ex that I could not make the July Payment as I have no savings at all, 40k+ on credit cards (the only house I could afford needed - and still does - a lot of work done), that I cannot obtain any more by remortgaging and the only source of money would be take my pension (it will be a limited amount as my pension pot is small as for the years together I was self employed I paid additional mortgage payments as opposed a private pension) or to sell the house I live in now, which I still have a 150k mortgage on). I advised my EX and the CMA of this - both were happy to wait until I got the options back from my pension provider. Yesterday I received a letter from the CMA telling me I would move to their collect and pay service... Anyway, my main point is how to determine when payments stop; I have spoken to a solicitor who advises me that it is a legally 'grey' area, the CMA tell me 'until we tell you to stop (currently scheduled until 01 May 2020)', and on the various GOV websites it states 'until A Level education or Pre-U'completes (no explanation or definition for what Pre-u is) OR when Child Benefit stops (how do I find out when this is) OR when child starts Advanced Level education (is this University?) starts. I have also read on Dads to write a letter and mark it as a complaint. At my age I can barely afford to live and certainly not enjoy living. I cannot afford to fully engage a solicitor - any clarification on any of the above points would be helpful (I have read the Legal Eagles posts and they help but do not clarify my questions as above). It is not that I do not want to support my daughter - I would have liked to provide for her Uni and post Uni - but at this point in time I will need to work until I am 70 and have very little to live on after then.

The most painful part is that the last time I saw my daughter was for an hour two years ago at my sisters funeral, prior to that I had not seen her for three years - apparently my ex tells me (by text) my daughter is happy with the a whatsapp message 'good morning and'good night' once maybe twice a day...
This may sound like a general moan - but I really am at the end of my tether.