Salts CaSO4 2.4g, CaCl 2.0g, MgSO4 1.6g plus a quarter tab campden. 15 min boil. Kegged with a half tab campden.
Based on boiling 1.05 gallonsliters at 1.046 for 15 minutes, this will decrease your wort by 0.25 gallonsliters, bringing your after boil OG to 1.057. You wanted an OG of 1.050. It looks like it will be over.