Once you have the copied IPO (let’s just keep it one IPO… easier) make it single user so it relates to (let’s say sphere.003) only. Now you go to the IPO window and click the lock. Once you do this anything you do to an IPO (grab, scale, grab one cv etc) will show in realtime in the 3D win. So if you select the LocZ IPO, advance to fr50, select a cv and grab it and move it up, then the object will move up in the 3D window. This way you can see exactly the effect on the object of the changes you make to the IPO.
Therefor, instead of splicing this part of the IPO to that part to get movements 1 and 3 and leave out 2, you can now just reposition each cv using the visuals in the 3d window to place them exactly.
(what I’m not sure about) is whether you can select Loc IPO’s for X,Y &Z then box-select all the cv’s on fr50 (xyz) and move them all together. It depends on LocRotSize of your particular objects when you added the Key. (it works for one of my .blends but not in another.