Several thoughts...
IF JM is responsible for MH then I expect the October 17th date is merely a coincidence. Even though it fell on a Saturday in 2009 (prime party night in most towns) it's difficult to imagine that it was planned, seeing how most crimes like these are based on opportunity.
Also, is it known to us if any DNA was collected from MH's remains? I don't know enough about it, but it seems like that much time in the elements would have greatly deteriorated anything present. If that is the case and the only DNA in that case is from her tshirt, then it seems like it will be harder to legally link that evidence to her assailant.
Finally, is it plausible that DNA results from JM's apartment (toothbrush, etc) have possibly hit a match on the MH case and prompted the warrant for the "abduction with intent to defile"?
I'm trying to review all the data objectively and not draw conclusions based on circumstantial evidence between these cases, but I feel that in regards to Hannah, JM's flight to Texas doesn't seem like the actions of an innocent man.
In any case, I truly find it unthinkable that anyone chose to violate these young women (or anyone for that matter). I sincerely hope that all of these families can find justice in these cases and that these dangerous people are removed from society. I know the empathy I feel thinking of these young women when reviewing the evidence presented here and that it is NOTHING compared to the pain and loss these families feel.
All of this is my opinion of course.