Ca++:Mg++ ratio, possible Mg++ overdose

Hi folks,

Since I stopped using Kent's mystery GH reagent, I've used Greg's CaCl2
and MgSO4 to tinker with my GH. However, I may just have made a
colossal boo-boo. To wit:

My tapwater is about 1 dGH. I up it to circa 4 dGH by dissolving the
Ca and Mg compounds hereinbefore mentioned. These I add in an
approximately 1:2 molar ratio. I didn't think about it for a while,
until I saw, somewhere, a reference say that 5-10ppm of Mg++ is the
target.

To make a long story short, I've apparently been overdosing Mg++
severalfold for about three weeks now. Before that the Ca/Mg ratio was
unknown, since I don't know the composition of Kent's GH reagent.
Anyhow...

This poses questions:
1.) Is my severalfold Mg++ overdose something about which to be
worried?
2.) In the future, I plan to dose Mg++ to 10 ppm and then build the
balance of GH with CaCl2; does this sound kosher?
3.) Does Mg++ overdose mimic other deficiencies? (K?)
Best regards from snowy NYC,
Trapper