Okay, I've been searching the web for a) how to use the bombsight properly, and b) more info on the different fuzes. Sadly, I came up with almost nothing so far
One thing I did find, however, was some pics about the blen's bombsight:
http://users.cyberone.com.au/clardo/..._armament.html
The sight is identified as a Mk IX course-setting bomb sight and the drawing suggests that there is more to adjust than I currently do (just alt and speed, while considering the sight being off, as mentioned above). Apparently, you have to look at the junction between those two rings.
A thorough explanation would be greatly appreciated!
As for the fuzes... the search has been frustrating. I've found heaps of pictures from collector's sites, but no info as to how they work. A short table would be greatly appreciated as well!