the patreon subscription is monthly, if you don't want next month you can just cancel (a fee when you join and every month after if im correct)
My country changed currency to the euro cause our original currency was used by only us and that was bad for worldwide trade, so we swapped to something more countries use
The transaction isn't that bad, as said the game is definetly not finished and after the main story is done they will for sure expand
When the game becomes pay to play you'll need to pay 7 dollars to get a patreon subscription when the update comes, and thats that(unless they decide to make you able to buy the game at a set price and get further updates for free, they did try to release it on steam after all)