Why are the leaves on my orange tree curling. Best shown in 3rd picture. Am I not watering enough? Watering about one gallon per day. Tree is 7 ft high and 6 feet in diameter.

Check for spider mites.

I water my container grown grapefruit that is only 3' tall a gallon of water a day. I suggest you water more especially
your being in sunny California , if you have a drip hose that would be great to use

More water may help. I have a Orange tree of similar size 7ft tall by 8 ft wide. In the dry hot months (i'm in San Diego) from June through August I water the entire 8 ft circle under the tree with 50 gallons of water per week. That's about 1 gallon per square foot of ground per week. Also to encourage deep root growth I water the tree several times in the same day (using drip irrigation) until the 1 gallon per square foot has been met. This slow constant water delivery will penetrate 18 - 24 inches into the soil. I then let the tree dry out for 6 days since I have read that citrus trees do like to dry out in between watering.