Caveat: This answer is based on general cooking experience, not an actual experiment.
I share your doubt about the toothpicks, especially as the force applied to the bacon when pulling them out again is concentrated on a small spot. If your bacon is crisp, it’s prone to shattering, if soft, probably won’t hold its shape.
I would skip the toothpick and use a slim stir of parchment around the perimeter of your bacon spiral, held in place with a piece of kitchen twine tied around it. The parchment both serves like a “cast” holding the spiral together and prevents the twine from being embedded into the bacon. If the parchment isn’t too wide, it shouldn’t interfere too much with the steam during baking. Just to be sure, I ‘d take the temperature down a mothnotch and bake longer.
Of course this is more work than just pushing a toothpick through, but assuming you are making the decoration for a smaller gathering, not a 250 servings catering event, should still be manageable. Alternatively, go for the toothpick, but make lots of extras so that you have enough even if a significant portion suffers some damage.