Iron contamination will sit on top of your protection product mostly. It turns red or brown because it is rusting. So it doesn't matter how much protection your paint has, iron particles will still do the same thing when present.
As for waxing the car 3 times per week, you did not mention what product you are using but do not assume that your wax is building up. When you apply wax or sealant on top of an existing layer of the same product, the solvents in the wax or sealant are gonna liquify the product already in place. It is very likelly you will have roughtly the same thickness of wax after you are done the second or third time. The only advantage I can see of repeating this process is that if you missed a spot the first time around, you are more likelly to have 100% coverage after the second time you apply it.
Common practice using wax would be to wax once a month, and everytime you wash the car, you use a spray wax as a drying aid to prevent scratching the paint while drying. Spray waxes are usually sealants or silicone bases products that will add some additional protection to you wax layer (or sealant).
Regardless, iron particules can still land on the car even with good protection. Some cars produce more than others, it depends on the type of brake pads mostly. German cars are the worst for this. They brakes produce an insane amount of brake dust, and brake dust contains a lot of iron particles.
