Don't expect it to come quickly. I was stuck in diamond until I reached about 750 hours. I managed to not fall out of champ until this season's rank reset. I'm back in d3. I'm not much of a grindy player though, I play quite casually and only on weekends and only sometimes on workdays. I am not home currently so I'll update this comment, or just post another one with thoughts on your one's game later.
Also if you want I could play with you a bit to maybe see first hand where both of us can improve, I'm in europe though, so only if you're in Europe too.