Re: 64 years old, $390K retirement package
"Should the compensation for wrongful termination be influenced by that?" In most jurisdictions, yes. If he had walked into similar or better paying employment he would have received very little.
Regardless, Dell acted disgracefully but got off lightly. They would have been better advised to settle rather than go to litigation as "plus costs" would have been a fair amount as would Dell's own legal fees.
"disparaging the company to customers" i.e. he told the truth.