We resolve two open problems regarding the Sherali-Adams proof system. First, we show that Res(2), which manipulates 2-DNF formulas, is exponentially stronger than Sherali-Adams. This provides a sharp separation in power between Sherali-Adams and the bounded-depth Frege hierarchy, as Sherali-Adams polynomially simulates Resolution. Second, we prove that Sherali-Adams is not size-automatable unless P = NP. This resolves an open problem on the automatability of weak proof systems asked by many researchers. Both of these results are obtained by using a new technique for proving lower bounds on Sherali-Adams degree via polynomial interpolation.