The slope isn't overly extreme and your rig is not very long or heavy, level your TT with something sturdy under your tongue, using your x-chocks along with the larger rubber chocks in front of (ideally) all wheels should suffice. We have the prior version of BAL in between the wheels chocks with the wider pads, although I would never solely depend on them on any severe slope, once we crank them in they have never got loose until we removed them via included wrench.
After 14 years of heavy use, our BAL deluxe locking chocks still eliminate 80% of movement when moving around our rig, obviously have proven durability as they have always been exposed to the elements. They have been run over by our HD truck and 33' TT TH a few times without any damage other than a slightly bent handle. One of the best mods for TTs and 5ers, my DW will simply not spend anytime in the RV without them securely in place.