Tell your reader ahead of time
If you end up missing days, that is OK. Usually i can only draw on days where I am feeling good enough to draw. It's much easier to draw if I have a video playing in the background. So you could try drawing while binging a show or watching YouTube or listening to a podcast.
It's hard to answer this one unless I get context. There is taste which is subjective. If your MC is a boy and readers keep suggest to change them to a girl, that might have more to do with their personal preference. But if you have a flaw, it might be worth making some adjustments.
Have a someone who gives constructive criticism. Instead of people telling you "this is bad" find someone who can articulate what is not working and give suggestions.
I think I am also going to recommend just posting your work. If you feel a bit fed up with beta readers, you could just go straight to just posting the story and making edits later if needed. It does feel like you are in a bit of a spiral.