Just to wrap this up for anybody with the same trouble: I got the splines lined up by feel, pounded it back in with a hammer on a long screwdriver set against the middle of the inner shaft flange. I know it went all the way in because if it went any more the flange bolts would interfere.TIP: put the flange bolts in place before you pound the shaft back in. I did not replace the circlip. I have had no trouble with it since then. In the mean time, I ordered manual hubs because I could hear & feel the autos disengaging / half engaging. I think that contributed to the circlips and shaft getting ejected. I also took it easy; I found its limit! Should've tried this first, as suggested, but I was panicking and distracted.