Your sail switch should be accessible from the outside. This is a link hopefully to a manual for your furnace.
https://myrvworks.com/wp-content/upl...ing-Manual.pdf
Not sure why your jack is not maintaining your rig level, but it could be a seal, or more likely another component in the hydraulic system. The popping you are experiencing is called stiction, and can be resolved by the addition of stiction fluid. This is a link to the Lippert page that tells how to add the fluid that will stop the popping.
https://lci-support-doc.s3.amazonaws...cd_0002091.pdf