The problem with measuring your DME instead of weighing it is everyone's cup or 1/2 cup is different. You should use a 10:1 water to DME ratio, which like stated above will be 1000 mL of water to 100 g of DME. This will get your starter very close to 1.040.
Wow...that's pretty deep. :drunk:
IMO, unless your water is totally screwed don't expect to gain 12-16 points like was posted earlier. Most people's pH is fine even before the buffer, unless you are on well water.