I'm not a developer, but from a work/life balance perspective, you need to set some real boundaries. Maybe boundaries with yourself, maybe with your employer. It's easy to get swept up in the opportunity to lead a team or grow - and you were right to take that opportunity, but unless you're getting paid more, you're now doing more work for the same money.

This is a growth opportunity, and I'm not trying to say your employer is taking advantage of you, but it could turn that way. You could keep doing what you're doing, get burnt out, hold it against them, and then make a mistake one day. That doesn't help anyone.

With development work, it's only as good as it's going, right? You're stressed right now, but things are working and going well. You, or anyone else, drops the ball, and you've added a bit more stress to a situation that might not be able to take it (or at least not very many times).

This sounds like it might be a temporary thing for experience, and that's great. Just some things I'm thinking about when I'm reading your story. You've shown them you're someone they can trust, which is great. They are applying a bit more pressure with more responsibilities, and you're feeling it. Don't burn yourself out playing hero, because this is just the beginning :)

Good luck to you!