Everything looks good in your picks. The spot in the case just forward of the sprocket is the usual place for damage. You can see how tight clearance is there, but yours looks good. Sorry about being the voice of doom. Actually, that little screw in the center of your counter shaft is the chain oiler adjustment. I would tighten that up all the way in, at least until you get your leak figured out. Also, there is a seal behind your sprocket that may be the culprit, but it is uncommon for it to be a major leaker. 3/4-1" maximum movement on the chain, as you described...