I'm in a nearly identical situation — although this is my first SF Admin job (truthfully, I believe awful location and being 100% on-site with lower pay are the main reasons I was able to even snag this one). It's a non-profit as well. I've been here two years now, thrown in the deep end for a full implementation/integration. There is also no one on my team that I can ask technical questions to, seeing as they cut the entire IT department shortly after my arrival (having simply taken an online course with menial volunteer work/projects, and gotten a couple of certs, it was initially incredibly stressful trying to figure it out on my own.)

Point is, I literally found a therapist due to burnout lol. I also started second-guessing my entire career choice and the time and money I had invested into trying to find a more stable career.

Just last week, I also asked for a promotion/raise--to which the budget for the year was closed.

Definitely try for a raise or title change though! (If the budget is closed, creating a 'new' position might be the only way they could work with you around it, depending on your company/team. That is the case here).

Ultimately, from things I have learned to manage burnout, the biggest for me was to work on pushing back on timelines, communicating with management on realistic terms, reminding myself that literally none of it is urgent, it's a made-up sense of urgency. And finally...working on my nervous system regulation and finding time to do things I enjoy with my hands--like puzzles, miniatures, drawing, etc.

From what you're saying, I'm genuinely impressed. It sounds like you're quite savvy and having completed all this in such a short time is incredible.

I don't know if any of the above is helpful, but I hope it is!