I think you did good! I think its a good looking gun, Yes the frame has cerakote, slide don't think about it! At the end of the day at least for me its easier to carry and use a gun thats 99% flawless over one thats truly perfect! I know its ocd but gets that first knick outta the way
I can't stand a seller to lie to a buyer like in your case. The good thing is that it's a 2009 production gun and has the real Tenifer in its metal. That makes it pretty much rust proof. If that coating scratches or peels off you'll still have a great gun. The slide stop, slide lock amd magazine release button being painted over gave it away as a "bubba" paint job. Either way a Glock made in 2009 is definitely worth $400. I think you did well.