re: Nearing 50 and Hit Rock Bottom

P90X is designed for 20 & 30 somethings.
Ole Father time catches up with us all.
But at 50, you are not a spring chicken BUT you still have a lot of good years ahead of you.

50 extra pounds is a lot to be carrying around.
Think of it this way, you have a 50lb sack of rocks on your shoulder that you are toting around every step you take. Up the stairs, on the job, down the street, in the yard, at the store...

As far as diet, try something like the South Beach Diet plan.
Our metabolism slows down somewhere in our 30s so remember sugar is not our friend.

Drop the milk and PowerAde zero. Drink water with some fresh lemon and/or lime.

As far as an exercise routine. Start out slow but steady. You are no longer 25 years old so ease back into a good routine. You could possibly injure yourself.
Start walking in the evening after work.
Get some light weights and do a few exercises 2-3 times a week.
Do some light stretching at first.

You will get there if you stay with it.