[mcknz]

Perhaps it's worth talking to a therapist to examine your relationship with your family?

No matter what the legal situation is, emotionally this is your company as well, and I can't imagine how hard it must be to stop working there.

Talking with an objective outsider might give you some perspective on how best to set boundaries, to be involved but still respected and properly valued for your work.

Although "snake" is a strong word, it may be apt -- it does seem that your father continues to use your emotional attachment to the company as a bargaining chip against you.