I'm glad to see you like it so much. I don't have a patreon or anything, I just started out as a game dev by releasing this game. Right now I'm studying too so I don't have all the time to work on Captivity.
So that 30$ per month wouldn't change much regarding development speed. (very generous of you btw). New stages are coming soon though, stay tuned! And I'm glad you like F.E.R, that one is my favorite too!