I can sit here and tell you everything that everyone else already told you. But in all honesty you will become a better grower from experience.... Next time give this a try, serious, no joke as your MH could be poo.
Veg for 21 - 30 days under your 1000w HPS and flower with the same fucker. Ill put money that your veg will come out better. See how that batch comes out next time, kind of as a control test to see what happens.
What i do fo distance with the light is put my hand under and feel how hot it is, as long as its not burning my hand it wond burn the plant. Then give an extra 1 - 2 inches just for cushion.
good luck bro.
Ive done it.