Hello and Help

Hello all. Someone. Anyone?
Married for 20 years. Three children. Separated now for 3 years.
When first separated, wife took two younger children with her and said she would make things difficult if I fought that. Eldest was 18 and she chose to live with me. Middle child has since turned 18 and has chosen to live with me. Youngest just turned 18, currently with mother.
We sold the house to split the assets 40/60 in her favour (I readily agreed to this because she had two of our children). At this point, no debts as I had almost paid off mortgage then did so when house sold.
I bought a small dilapidated flat with my share. She chose to buy a more expensive house than her share allowed by getting a mortgage. She could have bought a reasonable 3 bed semi two streets away from our previous home, but wanted more.
At that time she was working in the nhs. I had not worked for 3 years since the diagnosis of my cancer and , later the same year, my middle child's cancer. My daughter is now happily in remission and has been for 3 years. I had treatment but cancer remained and is slowly progressing.
I am still not in employment but I do draw a small army pension.This is my only income. I do have a small teachers pension (7years) My house (sold flat and moved to different, cheaper area) is my only other asset (150k) , furnished through charity shops and family donations. I have a £650 car. Two daughters live with me and are full time uni students.
She earns circa 40k pa with nhs, plus overtime, plus bank shifts. She has 16 years worth of nhs pension and 7 years of army pension from immediately before our martiage. Her house is worth 230k, refurbished with high end fittings, wall to wall bespoke wardrobes, new kitchen etc. She has a 10k Audi and a brand new piaggio scooter (3-4k). One daughter lives with her and is in full time paid employment.
On initial separation I was reasonable but now feel as though I'm being taken for a ride.
She has now told me that she has appointed a solicitor and is seeking part of my pension and back pay for maintenance.
I assumed that the original split in her favour was maintenance of sorts. I also paid a small amount (more than the 5 a week csa calculation) into my daughter's separate accounts until they turned 18 or had finished compulsory education.
She said in a message that she did not want to make this difficult and wanted financial mediation. I called her and got nothing but difficulties. I asked when can i expect solicitors letter and who arranges mediation. I got a rant about how she is entitled to my pension, how she has a mortgage, and how ill she is.(She has not been diagnosed with anything but regularly goes to the doctors with different ailments. New ones appear when doctors exhaust all procedures and find nothing. When we were married she would daily take paracetamol and cocdomol that she got from work, not prescribed).
I wondered why now, after 3 years she is pursuing this. Coincidentally (?) my youngest daughter phoned me to tell me her mum is now in a serious relationship and they are thinking about moving in together. They have told no one but my youngest daughter. It seems as though sheis keeping this secret and is trying to bleed me dry before she can be seen to be even more financially secure.
I can't see mediation going well because she will definitely lie if it benefits her. She is also adamant on having some of my small amount of money.
As a foot note, any on earning 60% of the national median wage is deemed to be living in poverty. I earn 38% and by any account am living in both absolute and relative poverty. Despite knowing this, and despite knowing about my illness, she is trying to bleed me dry.
I actually feel sick just writing this. I feel sad.
I am so sorry that it is a long read but it is as much to get my head in order as anything else.
What steps should I take, can i take? How can i better prepare myself, actually and mentally?
Please help.

If you cant afford a lawyer get to CAB and also go to doctor to get letter on your condition and how this is affecting you. Take notes and keep records of all interactions. Your needs are most important to the court and given your sitations vis a vis your wife i expect you can counter claim and ask for costs incurred. Please dont think you are alone and remember you have your children .

You are unlikely to be able to "counter claim and ask for costs incurred".

In family matrimonial proceedings one party makes an application and the court issues that application which involves both parties. There is no means to counterclaim as the Court will make whatever order is deemed fair.

The award of costs is rare as there is an underlying principle that each party bears their own costs.

Getting back on point it sounds as though you have already had a settlement but if this is deemed not to be the case, it sounds - on the face of it - as though you did not receive a fair deal.

Your ex making a claim for retrospective maintenance is probably a red herring. If you have not formally dealt with financial proceedings there won't be a spousal maintenance order. And if there was no referral to the CSA/CMS there is no outstanding maintenance for the children.

The claim on your pension might have legs but it is a two-way street. Why not claim on hers? What if her pension is worth considerably more than yours? If that was the case you could keep yours and have a percentage of hers.

All of these issues rest on the merits of your individual case and whilst your post was detailed, there will be other issues that need to be taken into account.

As suggested above, going to the CAB is a good idea as is paying for a fixed cost appointment with a solicitor. I would be wary of free advice (other than from the CAB or charitable organisations) as this is usually time limited and might not get to the nuts and bolts of your case which may do you a disservice.

Charles