So they are about 4 months old and the hens are mature and laying.
	
		
	
	
		
		
			They pester the hens non-stop & know nothing about chicken courtship. Just grab the comb or neck feathers & jump the hens who don't seem at all willing.
		
		
	 
This has nothing to do with courtship or fertilizing eggs.  It's about a hormone crazed immature cockerel trying to establish dominance over them.  In this circumstance the mating act is about dominance.  The one on top is dominating the one on the bottom, either willingly or by force.  From what you describe, it is by force.  
The head grab is part of the mating act.  It causes the hen to instinctively raise her tail up out of the way so he can hit the target.  Even if she is willing you can expect the head grab, otherwise there would be no fertile eggs.  But when they are being forced it also gives him leverage to control her.  In regular mating a head grab is not violent but when they are being forced it is.
When my cockerels go through this phase different things can happen.  I typically have a mature rooster in the flock, which you do not.  
It can be a lot like you describe.  My hens typically run to the mature rooster when a cockerel starts bothering them and he scares the cockerel off.  
The cockerels may force pullets to mate but leave the mature hens alone.  Unless it is right in front of the dominant rooster he usually doesn't bother stopping it.  If it is a mature hen, he will stop it.
When I don't have a mature rooster I still have a dominant hen.  Often certain hens may willingly mate with the cockerel, especially as the cockerel gets older.  But the dominant hen and maybe higher ranked hens will not.  If the dominant hen sees the cockerel mating a willing hen, she will usually knock him off to show that she is still dominant.  At some point he will mature enough to stand up to her and defeat her but that may take a while.
Each chicken has its own personality.  How strong of a personality for the boys and the girls has a big part to play in how this actually works out.  It sounds like your dominant hen is not particularly strong-willed while the boys are.
Eventually, when a cockerel matures it usually becomes a peaceful flock, the hens willingly doing their part and the mature rooster peacefully doing his.  Some never mature but it usually works out.  Getting to that point can be rough.
	
		
	
	
		
		
			The question is, would it be best to let him in the coop with the hens or keep trying to get him into the second coop with the other younger chicks? I don't want him to be tormenting the hens in the morning before I go let them out.
		
		
	 
That is entirely up to you.  Personally as long as no one is being injured I leave them alone.  About once every three or four years it gets violent enough that I lock the boys in a grow-out pen to grow until butcher size, then decide which one I keep for the next year.  Some people are so horrified by this behavior (that I consider standard chicken behavior within limits) that they immediately get rid of the boys.  
I will not fault you for whatever you try.  Just pay attention and if it isn't working out try something different.