The fact that I decelerate or not has nothing to do with what the clock reads at the time that I get to B. We will agree on what it says when I'm there regardless of my velocity and whether or not I decelerate.

Unfortunately no. See below for why:

Imagine that instead of decelerating, I simply fly by and activate a switch that stops the clock at B. I can come back and read the clock at any time -- it's been stopped. So, what will the clock read?

The problem here is that you and an observer on B will not agree on simultaneity. So we would need to clarify what you mean by "flying by and activating a switch that stops the clock at B."

There's an implicit assumption in this statement that's problematic: That you and your twin at Point B will both agree that the event "I flew by the clock" and the event "The clock stopped" are simultaneous. Observers in relativistic references frames generally will not agree on the simultaneity of two events.

So from a practical perspective, what will happen if you carry out this plan? You fly by Point B and activate the switch to stop the clock. The observer at Point B sees you go by and sees the clock stop showing that 100 years have passed since you started your trip, exactly as he expects. You see the clock approaching showing that very little time has passed...and you go by and see that the clock does not stop, but continues to age very slowly. If you turn around to figure out what the problem is, you'll see the clock fast-forward in warp speed, and then stop.

You can ask your twin at Point B why there was a delay and the clock didn't stop immediately when you went by...but he will swear to you that it did.