3.5 grams gypsum, 2 grams ca chloride, 1 campden tablet for H2O. Add 4ml latic acid to mash (Est. 5.4 mash ph at room temp).
Based on boiling 7.00 gallonsliters at 1.039 for 60 minutes, this will decrease your wort by 1.00 gallonsliters, bringing your after boil OG to 1.045. You wanted an OG of 1.071. It looks like it will be under.