He can ask, but he can't do anything to a judge that says no. Under the Constitution, once judges are appointed, their pay cannot be cut. The idea to to separate judges from influence by the Executive branch. Indeed, the idea is so strong that it is highly unlikely that the Executive ever would ask for a judge to resign. This is a good thing--if you were a criminal defendant, would you want the Justice Department, which is prosecuting you, to be able to fire your judge?
Federal judgeships are created by law, so Congeress would have to agree to create more slots. Then, Bush's nominations would have to be confirmed by the Senate.