Just had a problem with mine that might help . The inner tube was falling down with no load , it would jack up fine. Jacked the front up with a floor jack high enough to let the tube come completely out. It just threads to the rod that runs inside the inner tube . In my case it came unthreaded I think from raising it too high and it was not threaded in tight enough. My solution was to place inner tube back in and while holding it up run the motor to raise the tube . This got the thread started . Then raise it all the way till the clutch slips . Then take the head off and use the hand crank to tighten the thread even further . So far so good .
In your case , to get the tube off , do the opposite. crank the jack to fully extended . Then with another jack bring the front of the trailer up a few more inches so the inner tube is not resting on anything . Use the hand crank and try to extend the tube further , hopefully it will unthread the inner tube and you can clean and lube . There is not much to lube there , the only real place is at the top , there is a bearing where the rod goes thru the outer tube . If you remove the motor it will give access to the top of that bearing. good luck