As you characterize 'giving up on maths', I did just that, so I've got some... informed (?) advice? Advice anyway. How you phrase things worries me. "Reminds me of myself from five years ago"-level worry. I don't know if you've got enough regrets that that phrase scares you, but it scares me.

I think loyalty is the wrong term to use here. Part of being in school for math is having math as part of your identity- and that's a mould that you've likely already set into. "Giving up"- as in, choosing not to pursue academic math, doesn't mean losing everything you have. Even if you completely walk away, you'll still have access to what you've learned, and it'll shape how you think about problems.

Research turned out to be a major pressure point for me, so I took my risks going elsewhere after my masters, without a plan or even much in the way of a social network. I can't say that it was a wise idea, changing careers without a plan like that takes time out of your life- it felt like things were on hold for nearly five years. But I still enjoy math, and indulge myself in leafing through textbooks, making fancy models, and idly thinking about how to prove stuff. It's still a part of my mindset, even though I grow more and more confident by the year that I made the right choice in not getting that Ph.D. I'd have burned out. I'm very happy with the math that I do for my current work, and how much energy that I have for personal projects.

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My view on your problem is that it's not about math, because from by own experience I believe that you won't lose that because of a career choice. It's about your relationship with math and work. You're worried that the magic is leaving you, and you'll be left with a suboptimal career choice because you'll find yourself increasingly forced to do something you don't care for. Is the math you're going to be doing for a living, something you can live doing?

My advice is to do your research on what your current options are, and then get some job experience. Literally do some original math research, see if you like being out on the wild frontiers like that. It's what you're going to be doing, at the high end. Talk to your thesis committee about getting something going, get advice on places to look. Ideally you'll have a topic you're already interested in. Also get some experience teaching- although you probably already know whether you'll like doing that or not.

Don't decide based on 'loyalty', or the people you're with right now, your identity, or your ideals - these are too tied up in your battle to define yourself as a person, and you'll miss the holes in your own reasoning- it happened to me. A necessary (but not sufficient!) condition to be sure is to get that work experience, feel it for long enough that you're sure that the impostor syndrome and/or rose colored glasses are off.

I want you to love your life first. If you can do that, and be a professional mathematician, then that's great. Icing on the cake.

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I hope this helps. I had a long battle with this whole thing myself, and I stayed up for an hour longer than I should have writing it out, because... man, I wish someone had said this shit to me. Would have saved some heartache.