Im still trying to work this one through, but it sounds to me like you have one of two (maybe both) things going on. Either you have a bad horizontal aim motor or something is jamming/getting caught. The fact that you state there's a jerky motion of the light is a good indication you've got something out of alignment.
Before we go any further, just to be sure, take a look at the pic below. Look closely at the top of the highbeams....see how they're nice and level?
Yours should be (more or less) the same from about 25ft, and as you back up should stay aimed straight ahead.
Look
closely at the shroud of the low beam (the chrome piece around the glass eye)....if someone who didn't know what they were doing previously adjusted it, it can cause the projector shroud to jam up against the outer shroud. If it looks like you have decent clearance around the shroud get someone to turn the key on and watch when it moves side to side. If it checks out the next step would be to try your motor. They can be interchanged between sides but I'm not sure if the horizontal and vertical aim motors are the same. You should be able to easily swap them once you remove the housings from the vehicle.
Seeing as you don't have the headlamp washers, removing the housings is a simple task. Just remove the the 4 screws on the housing (theres 2 black ones right up front on the top, and 2 silverish looking ones on "ears/wings" at the lower back of the housing.
More to come as I'm still digesting this thread...