MacBook Pro4,1 upgrade OS X from Snow Leopard compatibility with iPhone 5S
According to EveryMac That machine can run any OS up to Yosemite.
Whether it will run it smoothly or not is a different matter.
Whatever the figures might say, I've never known a machine to run faster on a newer OS, with perhaps the exception of the jump from Leopard to Snow Leopard…. or the memory handling from Mountain Lion to Mavericks. I've yet to try Yosemite myself...

As far as I'm aware, you'll need the latest iTunes to get the latest iOS, so your phone at the moment is stuck in limbo. If you ever need to restore, you'll find Apple will no longer sign iOS 7 on any device that is capable of running iOS 8.

I don't know whether iTunes 12 will run on Snow Leo; there's one way to find out, but all the steps you are about to take are going to be pushing you firmly in the direction of Yosemite.
Edit: iTunes 12 needs 10.7.5 at minimum.

Another stumbling block is going to be actually getting hold of any OS other than Yosemite. Apple removes previous OSes from the App Store - though you'll find the listing for it, it won't download unless you have previously 'bought' it.

TL:DR
Apple want you to move to Yosemite, iOS 8 &amp; iTunes 12.
Trying to avoid any part of that is going to involve finding some dodgy download of Mavericks etc, or finding a friend who already has the installer.
Your phone will be in limbo on iOS 7, might work for now, but can't be restored without iOS 8.
iTunes 12 requires a higher OS than you have.