I think that assuming this person was at least semi-intelligent is probably a little more reasonable than assuming this "not-so-smart" cop came up with this elaborate suicide plan to make it look like a murder... Instead of doing something way more straightforward like just "losing control" of his car while responding to an emergency, similar to how most police die every year.
And I'm not sure about the veracity of some of your claims. If he took his vest off and shot it, the round would likely penetrate straight through it. Where would he have even done this at, to have been unnoticed, shooting at a bulletproof vest? Wouldn't it be clear from a lack of bruising and tissue injury that this is what happened? The coroner seems fairly certain he was shot in the vest.
Also, how does shooting a gun multiple times "at a distance" have anything to do with eliminating stippling and powder burns? If anything, that seems would cause MORE residue as more and more carbon and gunpowder is being built up in the barrel.
And that still doesn't negate that he'd have GSR all over him/his hands if he was shooting himself from arm's length.
Then you have the question of only two shots being fired, supposedly not from contact range, meaning his arms would have to be outstretched. How do you practically aim a shot like that, ensuring it goes in between your vest and body, to cause a devastating enough wound that wouldn't be recoverable from if your backup arrives in time? Especially after already having shot yourself in the stomach once? That would be a feat in and of itself.
Do you have a link to the bruising info? Yes, if he shot himself in the vest while wearing it he should have a bruise unless it was a glancing bullet that hit his phone clip as was reported in some reports I read. Where would he have shot his vest while not wearing it? Anywhere in the country? In my back yard I can shoot vests all day long (not that I do but I do target shoot). Just saying it isn't like you need some secret hidy hole to shoot things in this country. We are all just assuming he actually shot his vest that morning which we don't really know yet. But if the coroner did say he had bruising and the bruising was indicative of a very fresh wound then okay he just did it.
Stippling - It is difficult to explain on a forum with words. I will try.
I shoot my gun at my house at my vest. GP stippling is not on vest because I was far enough away. Not on hands now because some days have passed or I was able to wash enough off that later GP Residue doesn't show it. Or I shoot enough later rounds that the first round doesn't matter for GP residue on hand.
I go to another scene and unload several rounds. I now have quite a bit of GPR on my hands and stippling on my clothing. Standard stance for shooting would be different than shooting downward into torso so stippling would be different. But lets say I shoot while lying on my back. Stippling changes. GP falls in a pattern onto my chest which is different that it would be if I were standing up to shoot at a suspect.
He may have been kneeling to shoot at distance and to shoot himself. Pattern would change again. And all this is dependent on whether the forensics was gathered and properly analyzed for something other than homicide.
How do you practice an aim? Well I don't think you practice a suicide aim. But assuming they preserved the crime scene which I doubt they did they should have been able to determine which angle the gun was when the final bullet hit his torso. Whether upside down, sideways, the distance etc.... It wouldn't be too difficult with a standard vest to take your handgun and do it one of two ways. Either straight down from under your chin, holding gun parallel with body and shooting (assuming he was right handed) down and towards the heart to the left away from the right hand holding the gun. This would insure a pretty good hole in the chest, most likely hit the heart and lungs, major artery and wearing the vest may have even helped contain the energy but not sure of the science there.
Or he could have shot himself through the armpit hole in the vest. My only problem with the armpit hole in the downward trajectory doesn't hit the heart or lungs and would leave it more open for him surviving. All of this would leave GPR but if he shot already his hands are covered in it so not much help there. But stippling on the vest would show an awkward angle.
I am going to break this into another post to explain the GPR and stippling from the homicide standpoint.