I'm not sure if SAP need 10 or 15G ... either way, when properly looked after it will more than likely be fine

Do know that you can only keep 1 of them in that tank though. Besides that, it is indeed a very good option, and they're absolutely adorable. I have to warn you though, in my experience they're a lot more delicate than dwarf puffers (unfortunatly I lost all 3 of mine in during an ammonia spike

Still no clue what caused it).
You do indeed have to keep up with the teeth, and according to most it's nearly impossible to not come to the point where you have to cut them ( be prepared to cut them every 6 months or so). For now though, I'd give him/her 2 snails every day (Indeed, no trumpet snails), and some river shrimp once a week

That should do the trick I think
--Edit--
The snails you can easily breed in any tank of your own. I find it impossible to keep my tanks snail free actually

Most fish stores should have some snails for you and give them either for free or for a very very very small fee. After that, you can breed them yourselfs

Or rather, just stick a couple in a tank, feed it some flake or cucumber (not too much ofcourse) and they'll multiply in no time. Shrimp you should also be able to find in your lfs, though I'm not sure if they'll be cheap enough =/ Around here there's very price, but I've heard of places in england (don't ask me where now) where people buy around 15 for a pound.
Also, South Americans like to have some plants and vegetables in their diet

Try giving them algae tabs as well if you've got them
Good luck!