Feeding is OK, as long as the roots are established, and don't worry about the MG.
I am in MG moisture control, with about 40%MG perlite right now, and my plant is happy.
I would try and keep your PH at about 6.5, that's what I do, and just got a soil checker the other day, and my soil PH is right at 6.6
Just make sure to PH after adding nutes to your water, because it will change your PH.
(Usually lower the PH), and you should have plenty of light for now I would think.
My plant is 2 months old, with (1 month vegging under 100w), now under 300w of CFL's.
If it's a month old, I think it's OK to start feeding, but start out easy, and increase every other time.
If you repot soon, I would be sure to add some perlite, I have found it really helps, after not having any in my last 2 plants.