Yep or on #3, someone willing to help her cover up the murder that may have already happened. and also someone she probably had to contact via text or call and would have definitely been on LE's radar if they were able to get KR's phone records.
Excellent point about the phone records, and I'll add to your other point that, if he didn't actually help with the murder, he didn't just help her cover up the murder. He covered up her involvement in it at the cost of completely implicating himself. And did so perfectly, as far as we know.
Those kind of concerns are why a scenario with KR as a killer in a spontaneous jealous rage doesn't make sense to me. There are too many unlikely events that have to take place. To break them down:
1. KR gets mad at Faith, and takes the step of killing her (yes, this in itself isn't typically how those situations play out).
2. She contacts this theoretical male who's close to her geographically and relationship-wise, using a method police don't detect.
3. He sends her away to create an alibi, and she interacts with several other people (JM and MR, at least) who don't pick up on the fact that something's terribly wrong.
4. He is intelligent enough to know he can't just clean the crime scene and remove the body, since he'll never get all the blood. But he's still very savvy, getting up all forensic evidence implicating KR and leaving his own, performing several actions I don't care to dwell on and setting himself up to take the fall if he's ever caught.
5. He somehow communicates, without detection, to KR about how she'll have to find the body, how she should bring a witness with her, and what she'll need to say to police about certain things ("make sure you say you left the door unlocked").
6. He leaves and never resurfaces during the investigation.
IMO, that just all seems very unlikely. People who kill impulsively panic and make mistakes, they trip themselves up, and they nearly always leave contradictory forensics when they're staging a scene. KR would have to be one cool customer who got very lucky to pull it off.
If she's actually going to be a suspect, I think it makes far more sense as a carefully planned, premeditated crime.