Water the root zone you have not the root zone you think you should have. A-1 in my opinion is right. Watering 45 minutes in sandy soil as you describe your situation being is not the way I'd go about it. Get a Lincoln moisture meter from forestry products. Water 45 minutes and take a moisture reading. Do that every hour and you will find the next optimal time to water. Then start cutting back on the amount of water being applied until your initial moisture reading of the root zone shows the sweet spot amount in which you water the root zone but don't waste water that is just infiltrating below the root zone. Might also want to consider a fertilizer injection system that puts out a small amount of fertilizer with every irrigation. right now you are in a yo yo situation. You need to eliminate as much of the yo yo you can. Learn to do a cats cradle. (applause for weak allegory of the week)
I'd find a free source of compost and start a regular application program.