I wouldn't waste my money on led's yet. The technology and price are just not there.
As far as your other issues, over feeding is simple, just don't do it. I never start w/ a full dose and usually never reach the recomended amount on the package. Temps are a little harder to control. Without knowing your space it's hard to give any advice. I use a combination of a cheap fan tstat from home depot in the attic fan section about $25 and a fan speed contoler on my outside veg box in an unheated shed. If it's cold outside the box stays at my set temp with the only heat source being a 400watt hps.
With consistancy you'll get there.