Hi john,
I'm also not entirely happy with my barlow. I have the same sort of problem. My scope was collimated on Saturday night at Kulnura and seeing was pretty good. Satrun at 12:30 showed a terrible view throught my barlow. I had two images it was so out of focus. With my straight up 10mm it was crisp anf magnificent. So I'm interested in ideas.
As to your primary adjustment it sound like you're having the same problem i had. My scope did not appear to have locking screws until I realised that there is a cover of the back and the three screws you are looking at is probably to remove that cover and reveal the actual adjusting and locking screws. Took me ages to get the nerve up to undo those. The manual said nothing about a cover
cheers