That's an excellent post, Cypress. I hold a similar view of Terri and the dynamic between her and DY and KH. I'm just not quite ready to give her a complete pass. Like citigirl, I too think there might be a back story that hasn't come to light yet.
You said yourself that sex is Terri's vice, and I definitely agree. She took to MC quickly enough, and I'd wager her relationship with the LS was about more than shrubs and weeds. A MFH plot is either a very obvious joke or it's serious. I don't see room for a misunderstanding. Then again, maybe he's an immigrant. If so, the humor might not have translated well. He might've been a little unsure whether she was joking, and when the news came out about Kyron, he freaked. It's could happen.
Forget about the LS. Getting back to Terri and sex, is it possible she succumbed to the advances of another man? Someone she met at the gym, maybe. Is she so powerless to her vice that she went and got herself tangled up in a dangerous situation? I dunno, but that's where my thoughts have been for awhile.
Honestly, if Terri and Landscaper had a somewhat joking conversation about offing Kaine because he was, in Terri's view, being a prick or insensitive, then it probably seemed a lot less funny after Kyron disappeared. If Landscaper was in any way in trouble with the law, he might have been compelled to see it as a lot less funny. Should Kyron's disappearance change the tenor of a conversation had seven months prior, though?
Also IMHO, a lot of discussions about Terri involve circular reasoning, and I think LE, Desiree, and Kaine are employing this type of fallacious logic.
I try to resist comparisons because each case is unique, but Terri reminds me so much of Brenda van Dam.
Lastly, IMHO, either Terri did this alone or someone completely unrelated to Terri via any nefarious connection but known to the school and Kyron (a SO or RSO) abducted and killed him. IMHO, there's no middle ground. The more accomplices LE, Desiree, and Kaine imply or peel out of the woodwork, the less likely it is that Terri's involved. If Kaine was missing, then okay, maybe Terri could've convinced one or several friends that Kaine was abusing her and she had no way out. FWIW, I'm not saying she's accused him of being abusive, but I think that would make a more compelling argument for some women. This, however, is not that kind of situation, and I think it would be extremely difficult for Terri to find even one person willing to help her abduct, harm, hide, and/or murder an innocent child, much less a gang of child abductors and murderers. This type of thing would've taken resources and a lot of planning. The agencies involved in this case are well into the double digits, and with as careless as Terri has been with her electronic correspondence, I find it extremely difficult to believe she was genius enough to leave not a shred of evidence revealing the names of her accomplices. In many ways, this includes Dede, because Dede didn't come to the forefront of this investigation until after she stayed with Terri (some three weeks after Kyron went missing). So, in effect, she came to LE's attention not because of any questionable correspondence or any real evidence but because she befriended Terri.
Again, and as I've said many times, the theory is guiding the quest for evidence as opposed to the evidence guiding the theory. All IMHO.