Adaptor + stem = no weight savings, in my experience.
Instead, weigh your seatpost and compare it to one made of crabon. Unless what you've got is something like an Easton, be prepared to raise your eyebrows at the difference.
You'll lose another pound or more by going to a crabon fork. Go threadless 1" steerer and you can then use the threadless stem and a set of crabon bars for more simplicity & more weight savings.
Those forged crank arms weigh much more than later Hollowtech stuff- another pound, perhaps, and rotating weight at that.

"There is no bicycle problem that cannot be solved with cubic dollars."