At my current workplace I have a new manager who is keen to micromanage, bully and undermine me. They set me so much work I have to leave work everyday at past midnight. Despite the fact I was promised study leave when I took the job a few months ago, the new manager is keen to renegotiate this settlement and is threatening to take this away from me. The manager constantly comes to DIY remedies to my incurable mental health issues. My main issue is the micromanagement, taking away my management responsibilities and suppressing my technical freedom.
My senior manager (who I technically report to) is keeping an ample distance from my situation despite the fact they hired this new manager.
I have a very close relationship with those on the company's board of directors. I negotiated some key partnership agreements with suppliers and I know the systems infrastructure better than anyone else. I am keen to see a massive upgrade job I architected through and continue to have close relationships with the massive companies who I saw through the partnership agreements with. The CEO once told me to tell him if I have any issues with this manager as I think the CEO has a negative impression of them.
My new manager and another manager close to the board also attempted to demote me from Lead Developer, I managed to prevent this by telling the directors that if this was attempted I would resign so now my manager is attempting to do this through an unofficial route.
Despite this I have a job offer at another company ready for me as the company's first in house software engineer which offers to add $22 000 to my salary, I would have a 1.5 hour extra drive (though I have been wanting to move further away for a while). The company is more formal though (more of a classic engineering environement).
My company decided to extend my probationary period meaning I can leave at a few days notice. A director told me he thought extending my probationary period was unfair for me as my managers told me I was doing a terrible job (he blamed himself saying he failed to report back to them what I had done).
As I see things I have two options; I could resign and state my problems in my resignation letter (forcing my company to fix them or see the back of me), or alternatively write a quiet letter to the CEO stating my issues with my line manager and potentially CC in another director I am close to? If so how do I approach either one of these solutions?