Reading post some things are different to my case
Yes CSA can be absolute nightmare, but with help they can be sorted
On the MSE forum a CSA worker gave me valuable help, (she was owed a lot from an ex who totally refused to pay for anything), with my ex not being understanding at the time , and no she was not on benefits, and she was getting everything i was paying via CSA. and now i think it was the fella she was with at the time put her up to it, as we had an agreement.
Get your local MP involved.
Don’t swear and shout and rant at them on phone, no matter how you feel.
I was some times dealing with a cold hearted ■■■■■ at times (CSA not ex lol)
I tried agency work, PAYE at time
Then got a job with low basic but lots of tax free payments 
Now Ltd co and assessed at £5 a week… but paid more.
I was on the original CSA system, where there are so many problems.
But when my daughter wanted to live with me the CSA where brilliant with every thing regarding arrears and payments, but my daughter stayed at her mum’s as we agreed it was best for her .
Now my kids are grown up and working the stress is gone. although i have £200 arrears i don’t pay anything
my kids are 21 and 24, daughter was in education (part time collage) till 19 meaning i was liable for payments and son at 16 went for apprenticeship. But going from 2 dependants to 1 made no difference on original system.
And although it may seem i was trying to dodge the system i wasn’t, just paying what i could afford.and also wanting to treat my kids as best i could.
And CSA have nothing to do with access 