Congratulations - you're doing so well you must be stoked.
Saw your comments on exercise. For the first couple of weeks I had NO energy so couldn't even face it, but after that i went back into doing my normal routine, spin classes, interval training etc. I think the big thing is not to push yourself, perhaps start with short runs/walks and build up. But my CDC has never said that cardio is out.
With the stag do coming up I think that you're going to have to face up to the fact you're going to eat and drink, but you only get one stag do (hopefully) so enjoy it, and make sure that once you're back home you are straight back on those shakes! So difficult to fit a normal social life around this plan, but it's how you deal with the occasional "day off" that matters.
Happy birthday.