GoodGuy.....I believe you to be grieving, and, of course, rumination is one of the things that are a part of it....I would expect you to be grieving for the next several months, at various levels and intensity......all normal and expected....
I do hope that you are letting yourself to have access to your emotional self....as much as your intellectual self. Being male and an intellectualizer, at baseline, I hope that you don't keep your emotion on too tight of a hold.
Therefore, I am going to share , with you, the exercise that I call the "wailing wall". It gives relief...at least, in the immediate sense, and I have used it, myself. It works for those who actually do it....
One must first find a place of the privacy...such as the seashore, the edge of the forest, an isolated parking lot, the top of a hill or mountain...etc.
Then one pretends...visualizes...that the person/persons in question are seated a few feet in front of you.....
Then, one begins to say whatever they want to communicate to the person, straight from the gut. Totally uncensored, and no holds barred!
It is o.k. to scream and cry....let all the anger and questions just come forth. Let the hurting and vulnerable underbelly speak out!....
Scream until your throat is hoarse, and until the snot runs down your face.....
Totally good to sound "Krazy" . Curse the Universe or God if that is what you feel....
One must do this until exhaustion....or, that the intense emotion just runs out.....
There were times, when I was where you are, now, that this was the only thing that helped...
It allows the emotion to bypass the frontal lobes.....and you get to "reboot" yourself.....
Try it. It might be a little scary for you to think about doing this....being that you use your frontal lobes so much to protect yourself.....but, I encourage you, even more to do it, because you need it even more......