My situation

I started at this company 9 years ago. I started as a custom woodworker here and enjoyed my work very much. Fast forward 6 years, The shop supervisor and company Owners friend decides to bring in his son into the company. About 6 months later I'm asked to come into the office to discuss a promotion and I'm thinking "great" a step up! So I'm offered this new position as an estimator and engineer so they can take advantage of my many years in the trade. Once I take the new position, the Supervisors son is moved into my old position and given unlimited overtime (where I was never given any) and my new job has turned out to be a huge dud. I get jobs to estimat when they are very tedious or lack important information to complete where the salesmen estimate the easy ones themselves for twice my pay rate. Sometimes I go a week or two without any work at all and the Owner is ok with that. So now I'm sitting and languishing at a job I really used to enjoy.
I can't tell you how discusted I am with this company but I also see allot of this as my own fault for giving them the benifit of the doubt. And by the way, I got the highest review in the company the last time they gave them out so I'm really at a loss to understand this situation.