Can my employer legally cut all my shifts while technically keeping me "employed" as to avoid paying out severance?

No, if your employer is cutting your shifts without your agreement then this constitutes a constructive dismissal or a termination and entitles you to a severance package. Please use the following link to determine a fair severance package in your circumstances (severancepaycalculator.com/) and then contact us at the number below for a consultation with a lawyer to discuss your situation.