Re: 308 WIN BARREL LENGTH AND TWIST
First, Welcome to the Hide!
Now, as to your questions...there are already an enormous number of threads that deal with this exact issue in existance on the forums. You would do well to run a search using the search engine linked to in my sig line below where you will find a ton of good information.
The short of it is that you'll want a faster twist like the 1:10 to get the .308Win loaded with heavier 200gr+ bullets. Your stated 22" barrel length will be more than adequate and frankly, if all you are doing in close-range work (200yds and in), I'd go with a barrel a good bit shorter than that (i.e. - 18" would be as long as I'd go for a short-range rifle in .308).