other people probably have more experience and insight into this than i, but one thing that imideately caught my attention in your approach is the IC in norway. I would assume that when britain wants this, they take it, and othervise it seems a lot of ressources to me to secure scandinavia.
Have you considered gradually expanding the luftwaffe with a plane or two pr round in order to be a serious threath to the uk nawy?
Regarding japan, my experiences are that it is good the keep the nawy close and avoid to many ships gone astray as they are often too weak against 1 or 2 bombers plus perhaps a sub. IF you have a strong united japaneese fleet in close priximity to the us (within striking range = 2 spaces), then you would be more able to dictate what the americans buy (landforces to prevent a japaneese invasion into western us.
my comments are of course just some of the possibilities, but are gathered from app. 30 games and generally seem to work very well in my playgroup.