If by Saturday, July 4th, you had worked your 40 hours, then you would get 1-1/2 times your hourly rate, not double time The smaller, non-union companies don't pay double time as a rule.
It depends entirely on company policy. Some pay time and a half, many (including a lot of stores and restaurants) do not. Ask your manager or look in your employee handbook.
Legally it's straight time. Some companies give premium pay for holidays, but they aren't required to.
Depends on the company but is usually time and a half
