Ok, on number 1 he is looking up and it causes his forehead to get deep lines in it. I would like to see all of his hair too. It should either look obvious it was cut out or include it all. Also the lighting on his face is a bit hot in number one.
Number 2, is a B&W version of the same shot. It makes his skin look more even but the same issues are still there.
Number 3, is much better but looks to candid. It looks as though there is a bit of spillover light on his left side of his face but not enough to mess up the shot. Also the bottom of his face looks a bit soft.
Number 4 is your best shot and his too. He is sharp and the lighting is good and the lines are hidden on his forehead. It is a keeper and the best of the 4 by far.
Now, the above is my opinion and they are all really nice shots but the last is just that much better than the rest.
Camera axis is a tad high on 1 2 and 4, try to have camera at same height as his nose ( no down tilt or up tilt of lens when doing actor headshots)
The agent wants to see his look not your artistic touch. The lighting needs to be 1:1 , very flat. You did this well.
The agent likes black cloths ( your model/actor knows this ) . Remember that its not a portrait shoot its for an agent to evaluate a look and that is important stuff to generate work for the client.
A few rules are No hair in the eyes. No jewelery, No logo on the cloths, Very flat lighting .
Break the rules of portraiture, we tend to find the angle that they look best and work from there, but for there headshots and comp/zed cards its about showing the look they have.
Those who are very good at this (giving the agent what they need) , get a lot a referal work from the agent. Most agents will tell there client ~ Go to so n so to get your stuff updated. It can be bread and butter work.