CG and FR had become friends. HHG, and FR, were rooting for CG, within hours of K's birth, to be allowed to come see his baby. CG had hurt HMR's feelings so badly, earlier in her pregnancy, (I personally believe), that that is why she didn't want him at the hospital, and made the comment about CH had been there for her through the pregnancy, so he was K's father (loosely quoting).
JW had to have read that, and seen the support for CG, and the comment about CH. More than one have said that if JW wasn't at his house, he was at the R house or HMR was at the W house. It has been said that the Rs/Ms treated him like family. Not only was CH stepping into the picture now, there was a photo of a lovely ring set, that was posted. If that came to fruition, there goes HMR, S, and K (if she was his), living with another man. JW, who had been a part of the R family for almost five years, at the very least, was possibly seeing himself as getting rooted out. What if he felt angry about that? What if he felt more at home around the Rs/Ms than his own kin? Nothing would ever be the same, now that HMR had chosen someone else. He stewed on it, and became angrier and angrier over time, till he acted (with assistance).
Also, S would be starting school soon. What would happen to JW's weeks then (AW's too)? Good chance they'd be trimmed down. S would probably have been enrolled in public school soon. Probably 1/2 day pre-school that upcoming fall.
Just pondering on some old theories.