Congratulations M,(posted 7770 days ago)I was/am in the same boat. The Halifax accepted my f&f offer of 500 quid back in Nov, and sent me a confirmation letter stating that no further action will be taken against me with regard to this "debt", but they would now pursue my ex-husband for the balance of the (made up) "shortfall".
I think you have to listen to the others, and look after your own interests. Give them the money and get them off your back. As your health is bad, having these money grabbing, lying, heartless pond- scum hassling you for the rest of your life is not going to help any chances of recovery. And if even if your health was good, do you really want to go through this sh*t they are creating for the rest of your life.
If it helps your conscience, do what I did, pay your money, get your confirmation letter and then tell your ex-husband what the situation is and offer to give advice if they start to harrass him. At least then your ex-husband will have some warning of possible repercussions. Hopefully, after the initial shock, he will calm down, think rationally, and be able to prepare himself. You are not responsible for your ex-husbands life, but you are responsible for your own. Although I felt quite bad when I told my ex-husband that the Halifax BS (short for Bas*ard Society) would probably hound him now, he took it very well and said he would have done the same in my shoes.
Wrt your "Deed of Satisfaction." Some solicitors arrange half hour/one hour appointments for a set fee - say 20 quid for half an hour and any letters cost extra on top. It may be worth finding out if any solicitors specialise in debt law in your area and giving them a ring.
Get your Deed of Satisfaction, write out the cheque, and get on with the rest of your life. This is marvellous news and you have to take advantage of it.
All the very best luck.
Tracey