According to testimony, NEITHER parties kept their marriage vows. If we believe the FL story and the guy NC brought to the wedding, NC broke the vows first. But it's water under the bridge, imo. They didn't want to be married to each other. Being in a bad relationship can bring out the worst in a person. I'm sure if BC and NC were married to more compatible mates, their personalities would have been a lot different.
I don't get the HM thing. We know they had an affair. Ok, next? Why keep bringing it up. To me, it would have been a lot more relevant (and worthy of repeating), if there was any sign he wanted to have a future relationship with her. But there's NO evidence that is true. This doesn't lead to motive for me at all. Nor does the $75k life insurance policy. Sure, we know she hated him (with good reason imo - he isn't very likable in my book), but we haven't heard he hated her at all (he had affairs, very disrespectful, but a lot of husbands do). Sure, he disrespected her (a lot), but that's not motive? He desire to be rid of her was almost there - divorce!