Shouldn’t the bend markings be from note head to note head? This looks really messy:
The presence of the low E in the other voice is forcing the bend to flip up rather than drawing underneath as it normally would. It’s tricky to come up with a very general rule for these sorts of multi-voice situations - here it would be prefereable for the bend to draw underneath the note but that isn’t always the case.
A general rule can’t apply to everything, so it would be nice if it could be manually overriden on a case by case basis. Here I would like to specify that the bend angle has to be anchored to a note head at both ends.
You should be able to select the bend and flip it with the Flip command (or set the Direction property explicitly in the Properties panel).
Another problem here is that the playback also bends the low E which obviously is not desired.
The Flip command lines it up with noteheads, but now I have a downwards angled bend. I’m not sure of the convention here: can an upward bend be notated with either a down- or up-angle?
Yes, that’s fine - the angle of the bend doesn’t tell you anything about the direction of the pitch change. The notes themselves tell you that - the position of the bend is just chosen so as to avoid the stems:
