For right now? I'd skip the whole concept of "rules". Switch to "expectations". Rules are black-and-white, and that is part of where the problems come from. Expectations are flexible... we expect you to keep your room neat... what exactly does THAT mean? well... that depends on if you're 9 or 6 or 4, and on a few other factors too... but it allows for: rewards for improvement, for example, without actually being where you want them to finally end up.
Concept from the book: "Kids do well if they can"... Too many adults approach kids with the attitude that "Kids do well if they want to". Which page are you on? Do you see the behavior issues as defiance? or as a cry for help?
When you have a kid with hidden issues and challenges, its hard. You do NOT know what this kid needs. But if you try to assume that they "can" do all that you expect, then you're going to get the behavior problems. So... in addition to switching your mindset about what the behaviors mean, and reducing the rules, it really helps to decide which 2 or 3 "problems" are actually important right now. Its called "picking your battles". The other stuff... you have to find alternative ways to handle. But you cannot focus on all of it at once - it doesn't work.
While you're waiting for the neuropsychologist evaluation, do your own research. He's 9 - that's probably grade 4, which is a critical year at school. Hidden learning and other disabilities often show up at this point (not necessarily caught at this point... not necessarily ever caught... but they do show up). Dysgraphia, motor skills, verbal processing, auditory issues, dyscalcula, other things...
Did we suggest doing a parent report? Its documented (don't remember exact name) under Site Help and Resources - it will help you pull together the details you already know about your son and his issues, and will be useful when you see the neuropsychologist and others.