Hahaha. Good stuff golem. I like the hardcore Marvel bias. Juggs magical power might be a hindrance to Supes, but with Supes' speed Juggs would never touch him.
Hulk would lose quick. He's probably the strongest but not fast enough to deal with Superman. Supes flies him into outer space and hurls him toward the sun before Hulk can do anything about it. DD could stalemate Juggs, and then they could team up and pull a similar trick...they wouldn't kill Juggs but they'd win via ring-out eventually.
No it wouldn't, the forcefield makes Juggernaut from direct physical damage i.e. if Superman punched him he wouldn't be hurt. However if Superman grabbed Cain's arm and threw him full force the field wouldn't do squat. Juggy's powers are class 100 strength, massive durability, a force field that prevents all physical damage and once he gains momentum it's impossible to stop him. Unfortunately both Supes and Doomsday can move faster than Cain can think so a speed blitz full force punch or throw would take him out of the fight. And Hulk can't take either Superman or Doomsday on their own, together they crush him.