That makes me think, even more, that Mikey may have had extra keys made.
One of those visitors (or a friend of the visitor) could have let themselves into Terri's place that night. Maybe it was arranged for Michael to be at work when that person confronted Terri.
Michael may have been in shock, when he arrived home and he realized she was injured, yet alive. He would have needed extra time to think over his alibi.
I wonder if it is possible that Terri's "collapse" lasted 6 hours or more.
Michael may have been threatened by the fact that Terri was gaining confidence in her attractiveness. Maybe he was hoping to make her jealous of him, by subtly letting her know other women were willing to have affairs with him.
Actually, Schiavo handed out three extra apartment keys -- one to Ted Bundy, one to O.J. Simpson and one to a shadowy figure named "Tookie." Does this help your theory that Mikey didn't do it?
Remember Terri told her girlfriend that she was going to go to bed and pretend to be asleep with HINO came home. Does that fit with your scenario?
http://www.prolifeblogs.com/articles/archives/2005/12/schiavo_truth_a.php