It sounds like you are doing an I credible job under impossible circumstances.
Cherish the moments you have together either snatched during the day or at the weekend.
This is probably the most challenging situation that you and she have been faced with so face that and say, well done me..
If you are well paid and your finances allow, buy in what you can to take the load off, whether it is ready made food (doesn't always have to be healthy or unhealthy), a cleaner, a part time nanny.
Not being able to shut off from work between the hours you mention is really really difficult and I am so sorry your employers are unable to see how difficult this is for you and are unable to spread the load more fairly.
It really does sounds like you make the most of the time you have with your daughter. You don't need to be doing crafts or learning how to play the guitar together to make that time worth while.
Again, I am truly sorry that you have been so badly affected by this situation and that single mothers are indeed one of the most affected groups in all of this and many will have to give up a lot to make it through this.