Advice for an exhausted inexperienced engineering manager?

Earlier this year I switched from being a junior engineer with about 2 years of experience to a new role as an engineering manager and I think it's killing me. Since taking on this role I've inherited the full responsibility of making all the architectural decisions regarding our application, making many of the product decisions, managing a team of 3 extremely inexperienced engineers/interns, growing that team, planning sprints and being the main contact point for how all our projects are going.

This is all on top of the fact that I'm still expected to be coding, and because my team is so inexperienced (literally no one other than me has more than a year) nearly all the significantly complicated technical work falls on my plate. I've tried my best to delegate it but any time I've attempted to do that I've ended up spending nearly 3 times as long unblocking and mentoring my team. I love to teach and do my best to really help them figure things out on their own rather than just giving them answers, but it's gotten to a point where I simply don't have the time and am not sure if they'll ever get to a point where they will be able to take things off my plate.

I'm not sure what to do. I've received little to no guidance on how to navigate this role and the workload is exhausting me. I think I want to go back to being an individual contributor. I think I was pretty competent as an IC for my level of experience when I started this role (at least in my area of the stack) and I think that's how I even got here in the first place. But I'm very worried that I've been so badly burnt out by the crazy work load that if I move to a new company I just won't able able to perform the same way I used to.

I've managed to just barely keep things together here because prior to taking on this role I had written pretty much the entire application my team works on and I know it like the back of my hand. I know that's not a great thing to build your career on, but I'm worried that if I move onto something totally new that my brain just isn't in a place where it would be able to digest it. Even now I see myself starting to slip up more and more in increasingly dumb ways in a codebase I built from the ground up because I can't keep up with this workload. I'm so worried for when this really catches up with me and I fail in some serious way.

I just wanted to get some advice from others who have gone through similar things. How did you handle this? How did you heal your brain from the constant overwork? How can you make sure any new situation you land yourself in is actually better than the one you're currently in?

Thank you to anyone who takes the time to read all this and lend their thoughts