@dariana Hey there, I'm a writer who also battles depression and anxiety. I've only been published once, a short story this year, so I can't speak to earning a living (yet?), but maybe my experience will be helpful for you in some way?
1) For me, I write to help with my anxiety. I've always been writing, but when my mental health got really bad (I'm now on disability supports because I do not work) it became almost the ONLY thing I could do.
Specifically during the worst of my crisis I made 2 rules for myself: try to write *something* every day and don't beat myself up. The "something" can be the sentence "I'm too anxious to write today, so I won't." It just had to be words in a document. The great thing about writing is there isn't some gnome with a pencil eraser removing the words once they're written, so the pile of words only grows, it doesn't shrink. Thinking this way helps me feel less like I'm "falling behind".
If I don't write, I DO NOT beat myself up. There isn't an omniscient tally-keeper checking to see if I wrote the words for the day, it doesn't matter to anyone else but me, and those of us with depression and anxiety, in my experience, need kindness, if only from ourselves. I can't help doing negative self-talk, but I *try* to be kind when I don't meet my goals. This has been far, far, far more effective for me over the long-haul than being self-critical. It's better to "fail" and only write a few words each day than it is to hate myself and write nothing.
2. I've only had one editor in a professional capacity, and didn't have to ask for extra time, fortunately, so in one sense I can't answer this question, but in another sense I can: don't worry about editors and publishers until you have a pile of work for them to edit and publish. My strategy (if you can call it that) is to work quietly on my projects now, when there are NO deadlines except those I set for myself (and remember, I don't beat myself up for missing those). When we're new, no one is waiting for us. There's no one to disappoint or frustrate, no one to email or call, no conversations to replay over and over again in my head regretting that one thing I said or didn't say.
My feeling, though, is that the writing community is *filled* with anxious and depressed writers, and more experienced writers can probably give you better tips and tricks than I can at this point. My only advice is to work on your projects now, and worry about publishers' timetables *later*.
3. This is a tough one. I'd like to see a world where everyone has what they need to live, through basic income or social programs or whatever. I think we'll discover - when that world comes - that there are a lot of hidden artists out there with magnificent talent just waiting for enough freedom to explore it.
But we don't live in that world. I've only been paid once for my writing, and it seems impossible from where I am that I could ever earn enough to get me off disability supports. I'm writing anyway.
What I'm learning from my local writing community and from writers I've met and talked with online, though, is that there are millions of ways to be a writer. The only wrong way is to not write. The writers I know who write professionally mostly have alternate sources of income (job, spouse, disability support), but they also get paid to speak at conferences and schools through their local writers' union/federation/group, freelance editing for other writers, mentoring and running writing workshops/seminars/etc. It can be a juggling act to balance all these different streams, but they appear to make it work.
I also want to note that writing isn't like regular jobs where you clock in and clock out. Writers do need to put our pens to paper, yes, but we also need to live our lives, to witness extraordinary things, to day-dream, to night-dream, to hang out with human beings, to engage with the world, to rest and reflect. From this perspective, there is no "time off", because literally everything you do can be fodder for writing. Look at all the stories about writers with writers' block that already exist! Even not being able to write can help fuel your writing.
I know I didn't really answer your questions, and hopefully some more experienced and successful writers with anxiety and depression can chime in, but I do hope some of this is useful or helpful to you! Best of luck with your writing, however it turns out.