How does the PoS work?
If, say, i have an address with 10k XSPEC, does it mean that i should be getting extra 500 per year (5% inflation target), thus a 2.something XSPEC added every other day?
Tried to reverse engineer it, but things don't add up.
I think you got it right!

You don't need to reverse engineer anything though, everything is open source!

You might also want to ask your search engine about what Proof-of-stake is and how it works.