Haven't been on here in a while - Mollie Tibbets and the Watts family sort of did me in for a while, along with a death in the family.
The following are MOO, IMHO....
1 - Guys means NOTHING. I live in the midwest and call my daughter and her friends guys ALL. THE. TIME. It is regional.
2 - I believe the officer calling the suspect a 'coward' was a taunt.
3 - The recording really sounds to me like it has a *slight* accent? Maybe Hispanic? I don't think the sketch discounts that.
4 - There HAS to be more audio if she was recording. They are withholding it for a reason.
5 - The family has been told more. Frequently, that is the case. Asking media to leave them alone helps ensure they don't accidentally leak anything.
6 - LE knows who it is, or has a really good idea. Just need a final piece to have an airtight case.
To your points:
1. "Guys" means "everyone" in the midwest -- boys, girls, dogs, etc. I say, "Come on you guys, get in the house" when trying to round up my dogs. I live in Indiana.
4. More audio could be the girl's voices. If so, I thank LE for the editing.

I really don't want to hear their fear.
6. I feel LE know who he is and knows he lives or has family in the area (they expected he may have returned to celebrate Easter with family).
I wonder if the car they are seeking was borrowed. Since I feel they know who the BG is, the car isn't directly connected to him but may have been borrowed. I think they are hoping the person that owns the car will remember loaning it to BG and come forward.
I am also wondering if the younger sketch was discounted due to a false alibi and now LE realizes it.
I don't think it was someone the girls knew or respected or Libby wouldn't have felt the uneasiness to begin recording. They were creeped out by him.
I am confused though -- do they or don't they have DNA?
JMO and thoughts...