Changing tire size on same Venaci Rim

[seahorse12]

Hi,
I am having to change my tires very frequently (10K miles) and looks like I have high camber coz the inside of my front tires looses tread while the outer edges and even the center is intact. I am using Venaci VS-124 rims. Now that Im planning to use my car a lot more, I would like to change the tires. My tires right now are (on the front) 265-35-ZR19. I am wondering if I can switch to 255-35-R19? That would give me significantly better price and mileage rating on the tires.
I could get Kumho tires for $196each with 40K rating. Can I use the same rims and switch from 265-35/19 to 255-35/19?

Also, would taking to a shop to get the camber right be a good idea? How much should it cost?

Thank you all for help in advance