Electric Tongue Jack

You might try lifting the tongue with a manual jack to get the load off the electric jack and then see if if can be moved with a crank or electrically. I'm thinking that if the screw in the jack is bound up it could be stripping so be careful of it falling if it should fully fail. If you can lift the tongue with a manual jack then remove the electric jack and then lower the tongue onto your tow vehicle ball for safety. Then you can replace the tongue jack with whatever you have that works.