"Weak"...at the moment i can't see a place where he's weak...i thought i had overwhelming forces in the Solomons...gotta re-think of my understanding of the term "overwhelming ".
My definition of "overwhelming" is where you can easily crush your opponent at minimal loss to yourself. In order to accomplish that you have to have security of your Supply and Replacement lines, as well as superior Forces.
At this stage of the Game a series of island bases such as the Eastern Solomons, the New Hebrides, the Tongas and so on do not have that security of Supply and Replacements that the Allies need. They are too far away from Allied Supply and Replacements. And the Allies do not have superior Forces at this time, other than 4Es.
Therefore, you have to build up in anticipation of when you will start to achieve parity of Forces, which is Summer 1943 - if you conserve your forces ahead of time.
Essentially, thanks to the inherent Japanese advantages built into scenario 2, the nature of the house rules that you agreed to, and your inexperience with the WitPAE Game engine as it plays in pbem, you are in January 1943 essentially where the historical Allies were in January 1942 in terms of your ability to counter the Japanese advance.
There are places where you can start to build in anticipation of serious Allied counterattacks in late 1943 and early 1944, but small island chains are not those places.
I'll make you an offer - if you are interested, send me a private message and I will send you a copy of my current game so that you can see where I have built up. Many of those places are still valid for you.