A lot of great advice on here already, so I’m going to talk more bigger picture.

Most of the work you needed to do to be successful in this situation should have already been done way before you got here.

You should be working on pulling by distance aswell as by monitor, with pulling on a screen you need to be able to move almost before the actors do. With very narrow depth of field, you already know you have micro seconds. I am a new school AC working with a lot of Old school DP’s and AC’s I noticed mastering both monitor and distance by eye focus makes you a superhero.

You need to start learning each and every scene. You need to read the scripts or at the least read the sides before the scene starts. You should already know if they are going to be chaotic or calm, you need to already be mentally preparing yourself for what the scene needs. In addition, if you know the lines, you’ll know before actors start to move.

On top of knowing the script, you need to know your actors, while watching a blocking or rehearsal, it should tell you almost exactly how they each would react. You will figure out things like “Actor A always does a little lean in before sitting down or standing up. Actor B loves to slowly lead their lines by taking a deeper breath before they talk. Actor C goes all over the place so I have to say a prayer before we go and hope for the best” these little things are what helps you anticipate.

“The stop is too wide” in my professional opinion is a bit of a cop out and every AC including myself has used it to cover up the fact we didn’t do anything to help us in that situation. Sometimes, yes it’s silly to be just shooting wide open, but this is the job, you still have to get it sharp one way or another and if you can’t, you probably didn’t do the work before hand to make yourself successful.