Based on boiling 8.70 gallonsliters at 1.048 for 90 minutes, this will decrease your wort by 1.50 gallonsliters, bringing your after boil OG to 1.056. You wanted an OG of 1.068. It looks like it will be under.
Turn keg psi down to 5 to serve. Sweet and smooth brown. Could use more dextose for head retention.