I've used this program for years and I still get confused by it constantly. I'm finding that having only one effect column available in OpenMPT is somewhat limiting (FamiTracker in particular allows four). I'm not sure if there's a way to increase this number or not.
No, but most of the time you can get around this limit very easily by just being a little creative. The "volume column" can be used for many other effects as well, and instrument settings generally can help avoiding having to use volume, pitch or panning commands in the pattern.
Not to mention that VSTi effects can be controlled entirely through PC's which are not bound to effect columns at all like the Zxx). So you can have as many PC's on a row as you have columns that do not contain notes.
The Kxx and Lxx commands also allow you to use toneporta and vibrato together with a volume slide.