Salts CaSO4 3.2g, CaCl 2.0g plus a quarter tab campden.
Based on boiling 7.00 gallonsliters at 1.038 for 30 minutes, this will decrease your wort by 0.50 gallonsliters, bringing your after boil OG to 1.041. You were planning on an OG of 1.041 so you are right on track. Nice job!