Of particular value to me is your suggestion to move the jumping LH motif to its own staff. I think I may have asked about this in our prior correspondence, but wasn't sure how to approach it. Since the left hand motif naturally falls on the treble clef, is it reasonable/typical to include a second treble clef that is designated for the left hand?
Is is typical to separate the hands as much as possible, so that LH has the lower stave and the RH the upper stave. The actual clef is not so important, you sometimes see two staves with treble clefs (for high-lying writing) or two staves with bass clefs (for low-lying writing). Actually in 4-hand piano music this is more or less the norm, for obvious reasons.
If both hands must be on the same stave, which often happens, still be sure to make clear what goes left and what goes right. Typically, RH notes get upward stems and LH notes get downward stems. In some cases it canb be left to the pianist to take some middle note with the RH or LH but that should be an exception (happens often in polyphomic music though where one hand partly takes over the line from another hand).
I have mixed feelings about the ending. I'll give some thought as to whether or not I will try to rework it, but welcome other people's feedback on the piece as well as the ending.
There's no need for mixed feelings about the ending ! It sucks, not to put too fine a point on it. You can't just chop an otherwise nice piece off like that. Why not continuing the jumping motif for a while, gradually making the other hand's figuration ever sparser, all the while getting softer. Just an idea - maybe not very original, but anything seems better than this.