I'm looking into the kappa_gaussian unit test now, and I'll see if I can figure it out.  I started by changing everything in lensing.py to be what I think is correct (A above), and then, as you also discovered, the unit test failed.  So I'm looking into it in some detail to see if I can figure out what is going on.  It is complicated of course by numpy's x,y flip, which also confuses me!  I'll let you know when/if I figure out something that makes sense to me.