Welcome to the forum - it's good to see another 26.5 RLS owner on the forum.
We have a 2016 and it must be just a bit different - because there is no way I can put the chairs back-to-back, we have to pull the slide side chair towards the door.
As to a level, I've been toying with getting one of these:
But haven't pulled the trigger yet. We have the Lippert LevelUP automatic leveling system - so I don't have to get things perfect - I just have to know when it's WAY off.
We've only taken our rig out twice and both times the site was almost perfectly level so I haven't bothered with levels.
But I know there are others on the forum with experience with these large levels - some of it negative - so hopefully some of them will chime in.
Buddy Ray - Atlanta
Jayco Eagle HT 26.5RLS
Ford F150 Lariat, 3.5L V6 Ecoboost
Max Tow Pkg, 36gal tank
Reese Sidewinder and Reese Titan 16k hitch