@Hyre I do understand your anxiety. I've been a single parent with a mortgage, no maintenance payments, and struggling financially for a number of years in the past- and yes it can be very scary.
But the thing is, unless people are very well off, even in 2 parent/ 2 income households most people do worry a bit about these things. The relevant words to focus on are 'worry A BIT'. Very kindly, you appear to be completely
over-angst-ing about this to the point of not eating in order to ease those angsts and that will do neither you or your daughter any favours at all.
As others have said, have some savings to keep in case you are out of work - 6 months worth of your take home pay, or whatever you feel is appropriate, as a 'safety net' to help you manage your worries, but try to relax a bit after that. You need to enjoy life a bit as well as pay your Mortgage and Mortgages are not meant to be paid off in the short term.
If you can afford to overpay a lot on your Mortgage, you should be able to afford a 'reducing term insurance policy' to cover the rest of the Mortgage if something should happen - it may also cover terminal/critical illness diagnoses and possibly an income protection policy. A Financial Advisor can help you with this and it should help, if you feel that there will be financial protection if it is ever needed.
I took one out over a 5 year term a few years ago, to cover the cost of a £20k loan for a new car and other things, which I started to panic about after we had taken it out ( I'm a lot older than you, we are both retired and if one or other of us had died, the survivor couldn't have afforded to repay it if they did). Took all the worry out of it
I think you would also possibly benefit from speaking to your GP about your Anxiety levels which from what you posted are completely disabling you to lead a normal life with normal 'anxiety' levels. I do hope you can get some help for your MH issues, but make sure you tell them how badly you are angst-ing about this.
Take Care of yourself