1. I really like Lisa's idea of adding 30-60 minutes a day of walking to Alwyn's workouts. If you do those 3x week, you're getting the equivalent of traditional ST + HIIT. But it's still only ~ 180 minutes/week of total exercise.
2. As DCB said, 2.5 lbs. of fat loss per week is really, extraordinarily good. That's not rearranging deck chairs on an ill-fated transatlantic crossing. That's very serious body transformation.
4. It only matters if you keep it off.
5. That's why the key for anybody in your situation is to effect that transformation with a training and nutrition program that you can sustain. Three Cosgrove workouts a week is sustainable. (I know because I've been doing the equivalent for about 8 years now.) Three of Alwyn's workouts + a grueling HIIT program, at our age, just doesn't seem like a long-term plan.
6. We haven't talked about diet, but it seems to me, anecdotally, that the broad parameters of your diet have to be not just sustainable, but compatible with your training program. I understand that it takes extreme discipline early on to jump-start a serious fat-loss program.
But when discipline lags, like I said, the framework needs to be something you can continue -- a basic and easy-to-remember set of rules or principles that make adherence automatic.