Okay, my fiance is a vet. The following is not medical advice, but a recommendation that you seek some professional contact with a vet and soon. Under a spoiler cut
She's had plenty of people try to adopt feral cats only to get shafted, both financially and emotionally. They want to do the right thing and help an animal only to discover that it didn't get it's proper vaccinations, and end up paying a hefty vet bill when the animal comes down with something like parvo or distemper or worse.
My immediate advice, if you haven't already, is take the animal to vet as soon as you reasonably can. A checkup and vaccination round now can cost you signifigantly less than if you discover the animal has a health problem later.
Especially when it comes to teeth.
Shop around if you don't like the price of the vacs, or check into local municipal programs, or check with local shelters, as there are usually cheaper options than the vet.
Beyond that, I'm going to recommend looking into a product called feel-away. It's a feline pheromone, it plugs in like an air freshener, you won't smell it, but it basically well help set the kitty at ease in your home. It tends to work on feral cats extremely well. Rescue houses and foster homes typically use it as well.
Lastly, microchip or collar/tag your new friend. If the kitty was feral before, it may try to escape some time soon again, without an identification chip or tag that could end poorly.