Well I just reinstalled the diaphragm and glued it in place, and soldered the voice coil wires back down to the posts, and so far everything looks good. I'm going to let the glue dry overnight before I run some test tones through it to make sure it's properly centered in the gap, but I feel no rubbing when moving it by hand, and I get normal readings for DC resistance on the voice coil, so I'm going to go ahead and say the operation was successful.
On the subject of earspeaker position, that sounds about where I've settled on positioning mine. I initially preferred them all the way out, until I got used to the way the K1000 images.