Could be bent pivot. Endstone pushing on the pivot. Try jewels ON without the endstone.
Before stripdown to mainspring , Push any gear reachable, ever slightly, to supplement the spring's force,
Pour a pallat of lighter fluid on jewels when runing. Also on pallet arbor.
Are you sure impulse is in beat?
If the shaft is too long. You can always pack it with these sorts of washers. The large black type in this photo. Its always better to be a bit long than short. Just make sure you have good clearance of the face and the glass.
You could get one of each size from Cousins and by trial and error fit the one best suited. Also a suitable set of hands ordered at the same time would leave a spare complete movement and a repaired clock for less than the ebay item.