I've taken coon, deer, squirrel, and coyotes with a 9mm Carbine in the past. Expanders on small coons is going to be messy. A 'tougher built' bullet that doesn't expand should treat you well, but will obviously have an exit wound.
Not only that, you're talking pretty pathetic trajectory out of the 9mm Carbines. They don't really gain that much in a long barrel since they just don't have the case capacity to capitalize on extra burn time. Poor ballistic coefficient and ~1300-1500fps just isn't real handy, nor real powerful, when considering 100-150yrd shooting.
17 or .22 Hornet is a better option for you, or a lightly loaded 223rem in an AR is fine for a coon gun. 17WSM might be another option, but the only semiauto available is a Franklin and she sure aint cheap! 17Rem in an AR as well.
I've had a few of the Kel-tecs and 2 High Points, as well as briefly a Beretta. Accuracy isn't great, but if you're supported, hitting "minute of coon" at 100yrds is possible. I wouldn't say that, in my experience, the 9mm carbines are "minute of vitals" accurate at 100yrds though. Mounting optics on them is hit and miss. They're better now than they used to be, but expect to need to cobble together either super high rings or riser bases, etc. The factory "battle sights" that most of these have leave a lot to be desired. Serviceable accuracy, but not precision.
Personally, I'd be looking at different bullets in your 22WMR. I've called and ran hounds after coons for about 20yrs, thousands of masked bandits to my credit, and unless you're flinging bullets a lot farther than you should, the 22WMR shouldn't be "failing" on you very often, no moreso than I'd expect a 9mm to fail at least. If you ARE flinging bullets too far, somewhere in the 150-200+ yrd ballpark, then grab up a 223rem AR and knock yourself out. It sounds like you have a calling partner at least some of the time, so you might consider having them haul the 22WMR and you carry a 223.