This part is interesting. When I first googled the total loss rules for Kansas, I found exactly what you are saying above on several web sites but when I actually went to the Kansas DMV web site, the rule was "loss of 75% or more of fair market value". not "repair plus salvage". I 100% know that my insurance company is interpreting this a the only repair estimate must be less that 75% of the fair market value, they are not adding the salvage value into the equation. The 75% is not a firm number as the repair estimate is just an estimate and the insurance co worries/expects supplemental claims once the repairs start. Mine worked out to 73% but the 2% difference is only $800 and is a risk for the insurance co. SC DMV reads pretty close to KS:
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In your case, as the fault of the accident was the other driver, diminished value should come into the equation in terms of "loss of value" so it would at least seem to make logical sense that repair plus diminished value would be the threshold.
I don't mean to belabor this, its just that I've been dealing with my situation and the insurance co for 6 weeks now and I'm a bit like Rainman watching Wapner on this topic. I'm glad your wife and no one else got hurt and I hope you get what you want out of this.