Hello Shellb, I am so sorry that you are going through such a horrible time. I am not surprised that you are feeling so anxious & stressed. Is your son's ex GF receiving help from the Mental Health Team in her area? Having gone through mental health problems myself, (especially since peri hit me), she needs to be under the MHT &, ultimately, be willing to receive the help offered. Hard as it is, you need to focus on your own health right now to prevent it worsening. When our DD broke up with her longterm boyfriend in the Spring, we were very upset but she wanted to end it & we sadly knew that meant we had to cease contact with him too as it would have been difficult for her & would have prolonged the pain for him. I still feel sad about it.
With regards to your job, I can say from personal experience as a TA, it is rewarding but, it can be extremely stressful & NOT because of the children. Many schools are becoming like businesses with management to match. My old workplace was no exception & it was ruthless. I experienced a breakdown early this year & ending up resigning from my job in early Spring after weeks of being signed off sick (I had been unhappy there for a long time because of the atmosphere but, like you, didn't feel strong enough to make the change). It became obvious that I was just a 'number'. I do not know your circumstances but volunteering during the summer gave me the confidence to deal with the public again & change direction workwise.
After going through a dilemma last month over whether to start a TA job I was offered at the beginning of summer (but felt unsure about as time passed) or to carry on with a checkout job I had just been offered, I turned down the TA job. I felt awful for the school but it had to be done. After an initial hiccup, I knew I needed to give the checkout job a chance & I am glad I did as, although it is physically tiring, I am enjoying serving the customers & I leave the job behind when I go home. There are no extras required in my own time anymore. No having to try & be someone I am not, either. It is also for less hours than my old job. Yes, the pay is less but the pay in my old job was spread out over the year to cover the many weeks of school holidays (it was a private school) so the difference is quite small, considering that I am working for 6 hours less per week (I just have less holiday but only work 2 shifts!).
Most jobs are online now (especially with large companies) & there are plenty of sites which will help you with compiling a CV, if needed. It does seem scary but I would say, summon all the strength you can muster & go for it - if necessary, wait until October halfterm & apply for jobs online when you are away from that stressful environment. It just isn't worth risking your mental health for. Sorry that this is so long but I hope that this will help.

xx