First 1600ml starter for 15 gallons of IPA is not enough unless you pitched 3 or 4 tubes. Using sugar for a starter will make the yeast lazy and not want to eat maltose, so you have to overcome that effect now. And like you said, you thermally shocked the yeast with a 30 or so degree temp increase. Finally it can take a day for activity to really start showing. But, you do have 3 strikes against healthy yeast so I would be a little worried.