That's a pretty neat looking one-stick you got there. Get yourself some Stealth Strips and a cam cleat and it'd be really sweet...
After you remove your stick, instead of standing and leaning back away from the tree to undo your second wrap around your 8, try swinging down into the tree and squeeze it with your legs. That way you can take some of the weight off your rappel rope, that helps unsnapping the second wrap quite a bit...