I have heard conflicting things. personally I am growing all the way through with my MH setup (see grow journal below if youre curious!) anyways, I have heard people say they got denser buds from metal halides and had good bud production, and others say that you need HPS. there are a lot of people on the forums who have grown all the way through MH. if you just have a small operation I'd say keep what you have and invest your money on some other part of your grow that may be lacking (if you have any areas)
as for watering. Im 12 days flowering at the moment and I water about every 2 days. when the top 2-3 inches of the soil are dry (i check this by using a moisture meter. found at most places that sell garden supplies for around $5-7.) the best way to tell if your plants need to be watered is by checking the soil to see how wet it is all the way through.
I dunno about he feeding because I havent had any experience with your nutes but i do feed, water, water, feed myself! if it seems to be working and your plants arent getting any signs of nute burn then i wouldnt worry. if you start to see nute burn then youre probably feeding too often! 