I just read all four parts!!! Yippee!!!

What a wonderful tale!
Thoughts on the stuff mentioned above:
Yes, the time appears to be moving at different paces in the different universes;
Somewhere in the text of part 4 is a "be" that needs to be a "he";
In addition to the above-mentioned 'how will Clark cope with Lois having had a relationship with Alt-Clark'...which I think he'll be grateful for if it brings her back to him with marriage on her mind, there's the issue of Lois masquerading as Alt-Lois...while it may take time for Alt-Lois to like/love Alt-Clark, will she be forced to step into Lois's shoes as Clark's wife until she can recover the "year" that Lois has played out for her? Will Alt-Clark sleep on the couch? Sounds like the problem Tank created in the Future series....
I have to tell you, I'm SOOOOO impressed with your ability to resolve this emotionally without me feeling that the breakup of Alt-Clark and Lois is impossible. That you introduced the order of events (first, the unequivocal undeniable and irresistable feeling Alt-Clark has for Alt-Lois, and second, the opportunity for Lois to return home...after she's already decided she must step out of the way) was just brilliant.
I can't wait another day for the rest of it....Post it today when I have a nice Sunday to reread it a bunch of times before I get on the road again!!!!!
Best,
Sherry