Schiff can safely ignore any subpoena issued by the House. All the House committee can do is find him in contempt of Congress...and then refer the case to FJB’s D.O.J. and then...?
Yes. Criminal contempt of Congress must be prosecuted by the DOJ or the US Attorney for DC as a misdemeanor.
Civil contempt of Congress is tried as a suit in federal court.
Congress has for practical purposes given up its ability to prosecute contempt on their own.