Go to Stack page, right-click the lane you want to add your patch to and choose "Add part 4 - [patch name]". I suggest you check out the tutorial video about Stack mode.
re: Problem 2)
There's no standard for numbering octaves. Some use C3 for middle C (MIDI note# 60), some C4 or even C5 (Sonar). You can change this in Omnisphere by going to the Live zoom page and setting "Key select display format" to "C3 is 60".