22" is really short for a 7mm mag. With magnum calibers you need extra barrel length to give the powder more time to burn. I think 26" is standard for a 7mm, and I would consider 24" to be the minimum. With such a short barrel you lose a lot of velocity, which is the only advantage of a magnum over a normal round like a 270.
That being said, it's tough to complain about a free gun! I'd certainly take it, regardless of the barrel length. Unfortunantly there's not much you can do about the noise. 7mm in a 22" would be extremely loud anyway, but with a ported barrel there's no way you can shoot it without some kind of protection.
My advice is to get a pair of electronic earplugs. I have a cheap-o pair that I got at wal-mart for $30. They're small and work great.
But whatever you do, definitly don't shoot it anymore (or any other rifle for that matter) without hearing protection. Any high-powered rifle can damage your hearing with only a single shot, and your gun is much, much louder than the average hunting rifle.
Best wishes and congrats on your free Savage!