isn't that an easy one?
He is not beholden to the sabbath; the sabbath is beholden to Him
in the context He says this He gives two examples of the letter of the law being broken while the ones doing so not being accountable to it: David eating shewbread, priests working in the temple on sabbath. those are illustrations of His meaning
Not quite....not saying that you are wrong....but Jesus with his "I am" statements usually had something more specific in mind as to his authority and power and majesty.