I think the planning started with the large life insurance policy they could hardly afford, along with the If I were a Bird blog the day before, it continued on when Janet's car went to the shop and conveniently his VX was then parked elsewhere. They ate dinner, and then he decided to go to a pick-up group soccer, there are many other things that lead me to believe this was pre-meditated much longer than a "rage killing."
A new child and another one on the way is hard and scary for most men, especially when they are facing a trial for embezzling from a company, all the while knowing that at the end of the month he'll be jobless again. He couldn't pay his rent either but he was able to pay for that soccer game and he didn't miss a beat with the life insurance policy.
I think Janet's murder was extremely methodical right down to coming home to call 911.
He said she was blue and nothing, she was supposedly not even bleeding during that 911 call though. She stopped bleeding in 10 minutes?
He's told people she was cold, he told them she was warm, he told people he gave her a priest blessing, he told people he performed cpr on her. He can't have it all ways.