I could make a lifetime of shots like you describe with the .223 for less ammo cost than any 9mm carbine (new gun plus ammo) and have the huge benefit of more practice with the more capable gun.
BUT, if you want to justify a new gun -- get a nice one and have fun.
Is a subsonic hollow point round available in .223”? (Dumb question I suppose - I’m on the front end of this and just haven’t looked. Easier to ask?) Seems like anything off std. would be pricey and hard to get.
The only animal I ever shot (some years back) with the .223 was a good size raccoon. Cartridge — I don’t recall EXACTLY, but, pretty std. The round went clean through, essentially body-lengthwise not including the head. I definitely want less penetration than that. Less noise too, preferably. Could get a silencer, maybe, but may not be legal in my state - would have to check.