My estranged spouse dropped me from her company's health insurance. Is this legal? I am now uninsured as a result.

Under the new affordable care act, it may be that your spouse's employer is only covering her as an employee and is no longer offering spousal coverage.  An employer does not have to offer coverage for the spouse.  It may be that she would have been required to pay extra to keep you on the insurance because the employer is no longer providing coverage for you.