Wow! All of the answers you've gotten are very different, and I'm about to add another to the mix.
First of all, I stopped changing my kids diapers in the middle of the night long before 9 months. Only change them if they're poopy or soaking wet. Changing them just wakes them up (and me) more.
Second, if they wake, pick them up and feed them as soon as possible. I never let my kids cry in the middle of the night. If they are crying (especially at such a young age), it is because they need me. Pick them up immediately. There is no reason not to. It is very likely he is hungry. He really could be going through a growth spurt.
Third, if feeding him doesn't work, then you try other things. For us, it was bringing them into bed with us. That almost always did the trick. They just wanted to be close to us. Once they were in our bed, they were usually out like a light.
If brining him into bed with you works, I'd do it. There really is no need to worry about forming a habit. They change so much at that age that the only habits being formed are by mom and dad. Most kids who co-sleep will decide on their own that they are done.
Our kids both start every night in their own bed and they have since they were about 16 months old. Prior to that the philosophy in our house was, "whatever works," so they did begin many nights in bed with us. If they wake in the middle of the night and want to join us, they are welcome to. They don't do it too often, but the option is always there.
I would relax a little bit, and just keep trying things. You'll find what works for you.