A few points here Playdo....
System scale - having System Units at Inches and Display Units at mm is a bad idea. At least have them both Imperial or both Metric - preferably the same units.
That model is BIG - is it really 4'6" by 5'1" ?
Always model at the origin, then move into position when completed. Trying to model at an odd angle a long way from the origin just makes life difficult.
Be careful using the Orbit Tool (lower right corner of the Max window) - if you click-drag while outside the onscreen circle, you are changing the perspective viewpoint relative to the world grid, which again makes life difficult. Stay within the circle, or use Alt+MMB instead.
Finally - please put your Max version, and brief system specs, in your sig. This can be very important, especially in these non version-specific forums.
As for the model, I recreated it from scratch - booleans are always going to give you smoothing problems which can take an age to correct. Spending time on the original construction can save you a lot of time later on, and give you better results.
Attached file contains an exported model - import it, convert to EP, then either turn on NURMS, or apply Meshsmooth or Turbosmooth - 2 iterations should suffice in either case. I can write up the construction process later if you want it.
16355_srU69QVJ87e88vueFezi.zip
Max 2016 (SP1/EXT1)
Win7Pro x64 (SP1). i5-3570K @ 4.4GHz, 8Gb Ram, DX11.
nVidia GTX760 (2GB) (Driver 430.86).