The compression is fine. It will run as low as 8 to1 , maybe lower. Propane burns slower than gas. That is why it likes timing. Also why you can have much higher compression. Just add some propane till you can smell it. Then back off a little.
Check to see if the rod on the cylinder is bent. Take it off and you should be able to manually push it in and out. I am guessing it will get real tight when pushing it in.
I am at 22.5" to the bottom of the skid plate. At least 25 to the frame rail. So I must have a 6+ inch lift. Do you think 2" lift springs would get it down and still be able top run 35" tires?