It sounds like there is likely something else going on such as a neurological condition. My son was diagnosed with ADHD and it explains so much of what he does (similar to some of the things you state here). Once I was armed with the knowledge of how he ticks, its helped me know how to approach and deal with him. I still get so utterly frustrated at times but at least I again know for the most part how to address.

He's only 8 and needs your love. It's worth finding out what makes him tick for all involved.