Can't help you define jogging v. running. But my tack is to take as long as it takes, and go as slowly as I have to, to get to 30 mins... It's seriously not worth the injuries to rush! Speaking from experience... I'm happy for my lower leg mechanisms to gently acclimate to this kind of pressure. Been SUPER careful - have stayed at week 3 for three weeks! And may slip back further: did my first run outdoors in a while yesterday. After the first running round, I knew to go right back to week 1 - still, my calves are wicked sore today. Good thing: no joint pain this time! Will be slowly moving my runs outdoors, 1 run per week. (Hate missing out on the miserly amounts of sun we've been getting!) So may start all over again. Fine!
OP: If 90 seconds scares you, there's no shame in doing 60 for another week, or until those 60 seconds are a breeze (breezes?).
Legs: Am finding totally unanticipated definition along lower thighs and calves. Saddlebags and top inner thighs still resisting though.
Goal - 135 lbs
April 2011 - 145 lbs
August 2010 - 178 lbs
C25k, DVDs, swimming