Sorry, didn't mean to abandon you. Back home now. Are you measuring your moisture on a fresh split surface? Large rounds will take years to dry as long as the bark is intact. Are you able to isolate your tank to separate it from the floor to see how high you can get the temperature in the storage tank? If You've been burning large rounds for the last month, the first order of business is to do a thorough cleaning of the boiler then try to get some dry wood to burn. Check the moisture on a fresh split surface.