I think that is a very good point regarding taking a close look at the walls of the trailer. The walls are stiffer than the steel frame so will try to support the load as the frame deflects. They are lightly constructed (check out this video) so they are probably going to show damage before the frame does. Look for both flatness and wrinkling on the exterior and also for the the interior and exterior wall surfaces becoming detached. Also, look for the bottom of the walls becoming detached (lifted) from the floor. 

I'm optimistic for you, steel is very tolerant of deflection, and I don't think your rails were that much over stressed if any. You're far from the first person to forget and leave the rear jacks down while raising the tongue jack. 

4 inches is a lot of deflection, so surprise that trim started popping off. Did you happen to notice the sag you were getting when you heard the popping noises? 

Bottom line is that you were most likely at or a bit  over the limits for how much stress you would want to put on an rPod frame. The good news is that steel deflects a lot and comes back straight until it reaches its yield point, which will occur somewhere around the stress you put on it. Once it yields it will hold a permanent sag, so, as furpod suggests, see if your frame is straight now or not. 

The finish materials that came loose did so because they were not able to deflect as much as the steel, but not being structural they can be reattached. 

Thanks for posting this because it should help make it clear to all of us why the leveling jacks are not intended to be used to actually take the weight of the trailer. Even if the jacks themselves can handle it the frame cannot.