Oh goodness....I wish I had super stamina.....(any advice on how to get it??)....but yeah I hear you.
Preparing for the LSAT is the MAJOR reason I have completely revamped my diet and exercise. I will do anything to get more energy for this exam.
Do 2 LSATs in a row w/out breaks.
It sounds like everything is your problem right now. Look up one of the study plans. I don't think focusing obsessively on one section and then switching to the next section is smart.