1. But in this case the user is indeed a spammer
No and I'm saying this without even looking at the posts (still not enough time). Determining if someone is a spammer (aside from the very obvious, bots and such) is subjective at times. You might see him as a spammer, while someone else might not. That was the point that I was trying to make.
How long would it take for the user to be banned? If he is banned will the reports be valid?
Anyways probably your reports havent been seen yet since you said you made them this morning, it takes a while for mods to see them since there are many.
There's not a defined time, so I can't really tell you. It depends on a lot of things.