Can my employer withhold reimbursements and accrued vacation time unless I sign a severance agreement that requires service, indemnity, release?

I read: http://labor-employment-law.lawyers.com/wrongful-termination/Constructive-Discharge-An-Abusive-Atmosphere.html). It describes what I went through. I'm a 40-something Director at a startup. I moved family across country to work. I make decent money and was to vest 5% of company in stock options. Weeks after move, the CEO says "Former co-founder is suing me for fraud and collusion." Judgement goes against CEO. Why not tell me before? Then my colleague, a 24 y/o lead developer, decides not to implement anything I design. Says and implies I'm stupid. Flips me off in front of company. Implies that "old people" are stupid. I complain to CEO many times. Nothing is done. CEO silent. Says to me privately "I might have to let you or other guy go." 6 mos pass, abuse continues. I quit. Developer emails me to apologize. CEO says $7K in reimbursements and accrued vacation time is my "incentive" for continued services and a full release. Don't want to sign¿not for what I'm already owe