Fusing two atoms is not "a sun", sorry. It's the reaction that happens in the sun, sure, but it doesn't tell us how anything at a macro level about the sun (or gravity for that matter). That's all observation and theory until we can fly into one or recreate one that exhibits the same macro-level behavior.

For all we know there's something important we haven't observed about the sun's ability to consume its available fuel (whatever that mass is) and what happens to the exhaust products that could cause the sun to cool far sooner than we think. Who knows /shrug... not that I don't hope we've got it right in our understanding.

It's a lot more than two atoms, and all the various experiments leading up to them being weaponisable gave us all the info we need[0]. If we didn't know how the sun worked, the bombs wouldn't bang.

This by itself should be enough to pass the test of:

>> Have we experimentally recreated a sun and verified any of the theoretical models we have?

in the affirmative.

I mean, it's not like science requires 1:1 scale models.

> (or gravity for that matter)

Neither cheese, which is a similar non-sequitur.

[0] Including the fun fact that the sun is a "cold" fusion reactor, in the sense that it's primarily driven by quantum mechanical rather than high-energy ("thermo-nuclear") effects.

I'm not sure if this was first noted before or after the muon-catalysed fusion research.

Physics: the only place where someone looks at ten million K and goes "huh, that's cold".