The Kahr is finicky until you have it broken-in. You need to shoot at least 200rds through it, but as many as 300. You will know when it's broken-in, because it'll all of a sudden become instantly 100% reliable.
You could also consider a larger Kahr model, like the P9, CW9 or the TP9. All range from 15-18oz. Very light, and very decent quality.
I would definitely not discount the Walther and M&P. Both are highly rated. They're both good quality. Thing is that the Walther and Kahr are single-stacks, and the M&P is a wider double-stack. It depends on the ergos. The PPS is 19.4oz. Heavier than the Kahrs, but lighter than the 21.7oz M&Pc. If weight is seriously an issue, I'd be looking for a single-stack option. 7oz is a big weight drop, but 9oz is even more. Dropping 10-13oz is even better.
The other option is to consider a Smith&Wesson airweight revolver, but I'm personally a fan of autos and would never deviate from an auto.