Tom has his own density measurements that he uses; they are not the same as Fertilator. I have to use Fertilator when helping you because I use a scale, and don't know the densities. From my calculations and Fertilator, using the low end of Tom's method, you'd be dosing:
With a 65L column:
Mg: 0.09ppm - didn't account for how much CSM+B will add, but that's negligible.
Seems like a lot of PO4 to me, but it's probably nowhere near toxic levels. At worst dose 1/2-1/4 the KH2PO4 and see what happens.
Tom, what level of PO4 are you dosing on a mid to high light tank these days? I've been aiming around 1.5ppm per week based on my past readings, and figuring in for a 1-2 ppm added through feeding. Semi-accurate test kit says 3-5ppm.