So a couple of things that I've learned regarding the boil off. The best way to reduce things like DMS, and other nasty's is a vigorous boil. Now mine is a bit much likely, but I have no good way of reducing it other than cycling the heaters manually (which is perfectly fine).
Well here's another myth that will die. Excessive and prolonged boiling CAN AND DOES actually damage wort. Back in the day, pro brewers did boil off with long and hard boils that evaporated 15 or more percent of the original wort volume. Then they had the realization in the 70's, that energy efficiency was actually a good thing (oil embargo) and there was a flurry of activity in investigating wort boiling and what its effects were. They found out about what it takes to deal with DMS and other volatiles in wort. They also devised better kettles that significantly reduce the heat stress on wort and the amount of evaporation. Now, modern breweries are typically evaporating 4 to 10 percent of the original volume and still producing the DMS reduction they need for good beer. I'm not going to steal the thunder of my upcoming HomebrewCon presentation, but I've spent over a year of intensive study on this subject and conference attendees and AHA members will learn more about this subject and why they shouldn't be abusing their wort that way.
One effect of excessive boiling that may align with this thread's subject is that you can reduce the wort's Coagulable Nitrogen content too low and that can reduce head retention and possibly some body.
Checking wort pH at 150F means that you have little idea where your pH actually is. Calibrating the meter with room-temp calibration standards and then expecting the meter to report correctly at 150F, is folly. In addition, that offset between room-temp and wort-temp pH is variable. You can't (and shouldn't) apply it with confidence. Do cool off the wort sample into the 60F to 70F range to improve your measurement and avoid abusing your probe.
Denny, I agree that batch sparging can produce pretty decent efficiency. But in this case, I expect that the large amount of wort produced in the initial runoff means that there will be less sparging water volume used in the subsequent batch or fly sparge. Getting that water/grist ratio to a more typical range is likely to help either sparging method.