Yes, your brother is incorrect about .223 availability. It's everywhere and easily found. Walmart even has it.

You have to let us know what you're going to be using the rifle for first. If you are looking for a deer rifle, .243 is going to be the lower end limit. It's hard to say what you'd consider a "big kick" since you haven't been specific on that. I mean I have no issues with a 7mm mag or 30-06, but you may.