A voluntary resignation to avoid termination does not affect your ability to qualify for unemployment benefits. Your severance package will be considered deductible income and will affect when you are able to start drawing benefits, but will not affect you being able to draw as long as your previous employer does not contest your claim.
Each state has a different weekly benefit amount. It is based on your earnings during your base period weeks. You didn't indicate what state you live in.
Currently, $415 per week in Kentucky and $390 per week in Indiana. But how much you will draw will be based upon your earrings.