While of course it's possible to be overweight even on a healthy diet, it's somewhat unusual for a cat on a low-carb wet diet to gain too much weight. So maybe be extra vigilant to see if Sox is sneaking food, finding lost kibble under the fridge, licking plates in the sink, etc.
I would consider getting him a dental if the vet has noticed anything - no matter how minor. Dental issues are such a big deal for our sugar cats, and many vets (including mine) don't realize how directly the two interact.
As for when to consider restarting insulin, I agree with what Linda said in post #18.
And as for exercise - yes, it can temporarily raise BG during/immediately after play. However in the big picture, it is beneficial, both in terms of BG management and in overall health. Especially for indoor cats who tend to be much less active than their free-ranging neighbors. Both in terms of physical benefit and mental stimulation, daily active play is really important. My civvie doesn't like to play, so I have to throw treats down the hall and make him trot back and forth to get them. Gives me a little exercise too as I have to keep switching ends of the hallway so he'll go the other way! Sam has decided he's bored with the wand toys, so I've been training him to jump through a hula hoop! It's a little hit and miss still, but hilariously fun for both of us to work on this new skill!