I don’t even know where to begin but any help would be so very appreciated

No wonder you are struggling. You are currently being underpaid by £1632.64 a month, presumably since the start of your claim 4 years ago.

Your work coach is acting outside of their remit, and I agree with Poppy and Kimmy's advice here – you should definitely complain.

Each individual error on your claim needs to be reviewed by a decision maker, and you will need to ask for your work coach or case manager to refer it. Add a separate message to your journal under "About a Payment" for each of these errors.

1. Your UC should have included LCWRA from the start of your claim.
   This would add an additional £416.19 a month. More importantly, it would mean you are not subject to work search requirements, sanctions, or the benefit cap. Add a note to your journal saying:
   "Under regulation 19, I believe my support group status under ESA should have been transitioned to UC and applied from the start of my claim. Could this please be looked at as a priority, as I have been incorrectly subject to sanctions and the benefit cap? If you are unable to make this change, can you please refer it to a decision maker to review as soon as possible?"
2. Your PIP and your daughter's DLA should not be deducted from your claim.
   PIP and DLA are both ignored as income for income-related benefits such as UC. The only way these are being deducted is if, at some point, you reported them as income. Add a note to your journal saying:
   "I have been made aware that the deductions for "other income" are incorrect. The amounts deducted are for my PIP and my daughter's DLA, which have been deducted since XX (add date here). These should be ignored as income. If you disagree, could you please refer the matter to a decision maker?"
3. You have been incorrectly benefit-capped.
   As you receive PIP, you should not be subject to the benefit cap. I understand that this is a small amount on your current statements, but when they make the decision regarding the "other income," the amount will increase, so this is important to address. You should also not be benefit-capped due to receiving LCWRA, but until a decision is made on that, it is better to focus on the PIP aspect. Add a note to your journal saying:
   "I have just noticed that I have been incorrectly benefit-capped since XXX (add date here). As I receive PIP, the benefit cap should not apply to me. Could this please be fixed as soon as possible, as I am missing money that I am entitled to?"
4. They have not awarded the disabled child element.

As Poppy mentions, the "2-child-cap" applies to the child element, not the disabled child element. As your daughter receives the higher rate care DLA, this an additional £487.58 on top of your current UC. You can have this added yourself.

To do this, log into your account and go to:
Report a change > Children and other people who live with you > Make a change
It will prompt you to re-add your children. When you get to the child receiving DLA, be sure to mark that she receives this and enter the date the DLA started being paid. Once submitted, you will receive a notice that the change happened outside of an assessment period; do not worry about this, as it is automatic. After you submit the change, add a note to your journal saying:
"Dear Decision Maker, I first notified UC of my daughter receiving DLA on XXX (add date here) and was told that, because she is my third child, I was not entitled to the extra disability element. I have queried this with UC since but received the same response. I believe this is incorrect, and I hope you can see from the notes on my account that I reported this change promptly." The backdating of this element will be sent to a decision maker, and adding the note to your journal will provide them with the reason why.

To reiterate, you are currently being underpaid by £1632.64 a month.