I am new and my best range so far is 217.2 miles alt of 45k. Is that my limit at 80 feet above sea level with some trees?
Yes, according to [http://members.home.nl/7seas/radcalc.htm] for a totally obstacle-free horizon (rare !). [https://www.heywhatsthat.com/] can give you a more accurate answer including the obstacles in your area.
according to the numbers you provide, and the calc result, the difference can be attributed to
b. antenna quality