Good for you Kaity! You seem to be in a good place.
I don't know of any hard evidence that says that being on HRT for any specified time is beneficial for having FFS. And while it may be preferable to have your face cleared, it isn't necessary. FFS can be done for many reasons - eliminate brow bossing, rejuvenation through face and/or neck lifts, hairline work, etc. None of this demands one achieves a certain hormonal affectation. If you're ready, go for it!
As for getting FFS covered by insurance, that depends on your insurance carrier. I know a few people who have had it covered but many more who haven't. It pays to check and it pays to be persistent if you think there may be a possibility your carrier may have their information wrong.