I don't know that he was intending to live openly with his lover, just that he wanted to marry him.
This might be closer....more like wishful thinking than openly planning. "One day I hope to marry you" is vastly different than getting a marriage license. Do any countries in Europe actually allow/perform gay marriage? I thought that on this, the US was first.
I think the accumulated pressure of a failed business, declaring bankruptcy (did they lose the house in TN, too?) and the corresponding bad credit/lack of money, feeling like he's failed in many areas of his life, repressing his desires, etc. all bottled up inside might be enough of a motive. Some people turn to suicide. Maybe he turned to a secret life.
The following is blatant speculation on my part:
IF all this happened, then RS wouldn't be able to divorce Karen. The secret life would all come out, and he would lose his position in the community and with his family and friends (not to mention possibly disappointing his mother). He would never be the successful author he dreamed of being. He would possibly be shunned and an outcast. If, however, he could come up with a plan that permanently places him out of the country (as a missionary), then he would be free to live his life in Europe as he sees fit, but return to family and friends with his status (as a minister, etc.) intact. Well, divorce is out because the secrets might come out. Just maybe he was coldblooded enough to think he could come up with the perfect crime, murdering Karen, and have the perfect reason to go live overseas for the rest of his life (too many tragic memories to stay here).
If he could plan it so that everyone knew he was out of town (visiting son in TN), he could sneak back that night, murder her, and sneak back to TN before anyone noticed he was gone. Maybe he even had a contingency plan in case he had car trouble or is otherwise caught (he conveniently leaves his prescription or laptop at home and went to retrieve it that night). Maybe that's what he told Karen. And then he does the unthinkable and murders her, tries to make it look like a random act of violence (smashing the window, wrecking the house). Maybe it's particularly violent because, deep down, he blames her for his failures, his inability to live the life he wants to live. His hair and DNA should be there anyway since it's his house, so no real need to worry about trace evidence at the scene. Somewhere on the way back to TN, he ditches the murder weapon and changes his clothing (which were likely very messed up). The next day, he knows Karen is supposed to take his mother somewhere, so it's likely Karen's body will be found rather quickly rather than days later (allowing her time of death to be determined more accurately).
Voila, he has the perfect alibi (out of town), he has reason to leave the country and live his life as he sees fit.
Again, I don't have any evidence to support any of this. JMOO. I think Karen was completely blindsided by this, as was the church. If you listen to the interview with her coworker, she supposedly always talked very lovingly about RS. So very, very sad.
