JRK

Loosen the adjustment nut and back out the stud approx 3-4 turns. Now, coat the threads with pipe dope and rest the band (tq to 72 in lbs and back off 1 3/4 turns) Tq lock nut to 30 ft lbs. That should get you where you want to be.
As far as the leak, I don't know, The only reasons I can see a leak from there is either the lock nut is left loose or the case is cracked. Fluid can travel up the screw threads, but not to that level of leakage. Have you checked the front cooler fitting, which is right under the band adjustment? The shop could have goofed something there when pulling the unit.