Well if A isnt unscrewing from the block, then Im not sure that teflon taping B will help. My reasoning for this is, if B didnt seal against either A or C and it leaked, the O-ring in A would still be sealed against C, and stop oil from draining out of the block. Does that make sence?
As for what I meant about teflon taping B, just wrap the tape around the external threads on both ends of B. These should be the parts that thread into A and C.
On my kit I used no teflon tape on my equivelent to B, and didnt have a problem. If you do try it tho, be mindful not to block any of the passage off. That could obstruct oil flow.