Your builder friend is giving you bad advice. Styrofoam doesn't cause condensation. Water vapour does. You can use styrofoam anywhere you like, as long as it is the vapour-impermeable type, and well-sealed at the seams, with a drainage pathway behind it. The previous owners must have not known the proper steps to take.
If the dehumidifier isn't helping, it's likely not an inside source of moisture, so it's possible you've got water vapour coming right through the brick itself, and condensing in the warm indoor air. One way to prevent this is to apply insulating sheathing to the ~exterior~ of the building. Styrofoam is fine, as long as it's the blue stuff that won't permit vapour to pass, and is well sealed at the seams.
Then you could stucco right over it. Or you could do siding, if you go to the trouble of applying strapping first.
Alternately, you could put strapping on your interior wall, providing a channel for the moisture to drain through, and drill holes in the outside of the bricks, at the bottom of the wall. Then put blue styrofoam insulation ~over top~ of the strapping (not in between), another layer of strapping, and drywall over it. Be sure to plug up any seams in the insulation, and any bypasses such as electrical boxes. Use spray foam for that.
That would bring your wall out 3 inches, presuming you'd use standard 1x3 strapping (really only 3/4 of an inch thick) and 1 inch of foam, plus half inch drywall. You could also slide another inch of foam between the boards of the second strapping layer, bringing the R-value up to ten. That would keep you toasty warm. :-)
