I'd also like to know which engine and which radio you're using. (It helps if you give more info.)

But it's very unusual to experience successive problems like you seem to be having. I've heard of cheaper engines having air leaks around the carb, and it's usually an easy fix. The radio issues really do sound like battery pack problems, or something in your plane causing interference. (You don't have a steel cable running from the servo to the carb do you?)

At least the Hobby Shop owner is treating you right. He could be saying forget it, your problem. []

Good luck, and let us know what happens.
Dennis-