I would recommend you get a jug of 5% fuel and mix it 50/50 with yours. This will give you 15% as a result. Be sure to use clean and dry containers and keep lids tight to keep moisture out. Buy 10 or 15% in the future. The higher nitro MAY be making your needle setting more critical but I won't swear to that. Hopefully you have not fiddled with the "idle" mixture since all was running OK. If not, you should be able to quickly get back in tune, especially with a little experienced hope. BTW, most trainers don't need to be tweaked to the max, just close. You're not racing and probably flying reduced throttle most of the time anyway. Stick with it.