CRAZY! IS to UC, Receive PIP but asking to WCA?

This country is bonkers. Apologies in advance for the bad grammar, I'm yet again worried and quite jittery. My daughter is very unwell suffering with a rare bone disease while I'm broken after caring for my mother and now require help myself.

Hope you understand what your about to read, if not, please ask for clarification.

Background information: My wife is a carer for my disabled daughter, she has been since last year and continues to be to this day.

There's several issues which I'm trying to address. Back in February I informed DWP and gov.uk I was no longer able to care for my mother due to my own ill health and to stop carers allowance. I received confirmation via email receipt that the change had been recorded. I also called DWP direct pointing out I am no longer a carer but my wife remains to be a carer to my daughter. I am told as the qualifying benefit for IS is still in force (as my wifes CA claim) nothing needed to be changed, and if anything was required we would receive a letter as I had reported the change online via gov.uk.

Due to my poor health I applied for PIP when i ceased caring for my mother and was recently awarded the standard rate.

In May, I am still receiving carers allowance so fill in another change of circumstances form on gov.uk pointing out I have already advised them and to please stop paying me.
In June, I'm still being paid. I get my mother to call them directly and she advises them I am no longer her carer as I'm unwell myself. Carers admit they've made an official error and no back payment would be due.

Roll on last week and we have a phone call stating our housing benefit is being stopped and advised to call DWP to find out why.
We call DWP and told as I failed to notify them that I stopped caring for my mother in February, I was no longer entitled to IS and would need to make a new claim for universal credit. I am also told I likely need to pay for the overpayment of benefits from February until October!!!

I explain that I had informed them, but the advisor stated I need do nothing. I am informed there is no record of contact to DWP, however there is message from carers showing al official error had been made on carers side. I also have the email receipts from gov.uk.
I explain I would have nothing to gain by not reporting it as my wife held the qualifying benefit of carers. I was told to wait for the calculations of overpayment and appeal. This sounds so wrong.

Issue 2 - We are now moving over to Universal credit. I explain I receive PIP and unable to work. I am now being told I need to attend a Work capability assessment? I've just gone through hell with my PIP claim now I need to convince another health professional I am unable to work with a WCA. Seems bonkers. Its crazy my carer does not need to look for work but the very person they care for (me) has to assessed for work? Surely, this is not correct? Am i expected to take along my carer to a so called job.?