I havent read the whole thread because im pressed with time...... but if i can offer my thoughts.
a) Think gut...a gigantic part of the immune system
b) Study pro-biotics and start taking them.
c) Beta-glucan
d) If your taking a baby aspirin a day maybe switch it out for a potent garlic supplement
e) NEVER EVER EVER wipe your nose, itch your eye, or touch your mouth at the gym....if it is an absolutely neccessity itch your eye with a peice of your shirt (upper arm sleeve) or part of your shirt you know hasnt touched anything (shirtwaist near the oblique) -- as soon as you get home (or even at the gym) wash your hands thoroughly and then use sanitizer. Do you know how many people leave the gym and go home and make a shake? They touch the side of the glass, itch their nose on the way home, itch the corner of their mouth, drink that shake from a glass that their fingers have picked up (that handled all those bars and all those grips in a gym where 1000 other people have touched)
In fact if anything above i would make e the focus. if you are anywhere itch your eye or your mouth or your nose with your pinky finger. Why? Because you pick up things and turn doorknobs and touch everything with your other fingers for the most part...pick up a spoon, a fork, is your pinky touching it? Thats the finger in an absolute neccessity you use to rub your eye with. Take these precautions to heart and remember that sick people come to the gym all the time before they are no longer contagious. Take the precautions that you need to take and think about that.
I always use the waist of my shirt down along the side near my buttock if i have to itch my eye in a gym and there is no other option....it is little stuff like that which will make a difference. I developed a gameplan about 10 years ago when i was getting sick all the time and I had enough of it..... Im not a germaphobe i just make sure i stack odds in my favor.