I think 90% of the time ground loops can be traced back to the incoming TV source outside of the building and it seems to me like most everybody spends all of their time indoors looking for these loops. Randy if I were in your shoes I'd take anything the chucklehead CATV installer said with a grain of salt and go outside to the incoming CATV source and physically inspect each and every grounding block, nut, bolt and wire with a tug of pliers or a tap with a hammer. I'm betting you'll find a connection loose, corroded or not connected properly.
If you do that and properly connect the wires using the CATV grounding diagram linked below I can pretty much guarantee you that you'll solve your grounding issue, until the chuckleheaded satellite installer installs the satellite dish.
CATV Ground DiagramRegarding the sub, put it through it's paces and if something's not right I'd certainly give Axiom a shout.
