I lost all respect for Mitch...
...when he tossed the gun to SLJ. The move was totally contrived as "now let's crank up the tension." I kept waiting for something like the gun being empty, or Mitch having a bulletproof vest on (though then the question is - where did he get it). But "a homicidal lunatic has a knife to your wife's throat so you toss him the gun"? Uh, no.
We can talk about the risk of SLJ slashing her throat if you shoot him, or even accidentally shooting her. But how a reasonably intelligent guy who's been advertised as being able to read people thinks that handing SLJ the gun is a good idea just fails to be convincing.
I would've been much happier with either Mitch shooting SLJ, or them at a standoff until the detective shot him from behind.