You have to remember, a broker gets paid somehow. And that somehow is lurking somewhere in your wallet. That said, a broker will be able to find you options at lots of different banks. They know what's out there and can help you with the process and options. A good broker can be more they worth the fees paid.
As far as all the options, the way I think about it: points are a gamble (I don't gamble), shop for low rates, and negotiate all fees (including closing costs) as close to $0 as possible. Banks bundle and sell of mortgages. Why would they do that? Maybe the interest paid on the mortgage isn't that valuable to them, so selling the loan allows them to get their money back and available to loan again (more fees, points, closing costs, yeah!) to the next borrower. Something to think about.
Oh, and hopefully that $350-400k price range will get you just "enough" house for your needs. The bank will tell you that you can afford much, much more than you truly need.