Like2fish, welcome to the forum.
Poor MPG while towing is normal. I get about the same numbers you are. I keep my speed between 60-65. It helps with the MPG and the trailer tires are only rated for 65 MPH.
I only worry about leveling when the refrigerator is on or going to be turned on. Other wise I block the tires so it won't roll away, slides in and as long as rain water is running off I'm good.
Russ & Kim
2014 Alpine 3600RS
2007 Dodge Ram 3500 5.9 4X4
2008 Harley Davidson Road King 105th Anniversary
(2011-5 bad year)(2012-40)(2013-45)(2014-23)