Setting up a click-hold-drag and release action triggered from a MetaGrid Pro button

I'm trying to automate interaction with a knob in Cubase. MetaGrid Pro (MGP) is an iPad-based control surface app that connects to your Mac via a companion app called MetaServer. One of its button types is a momentary latch — it fires one action on press and a separate action on release, similar to how a physical button works when held down.

What I need to accomplish is:

  1. On button press: move the mouse to a specific location, click and hold, then drag upward slowly over time
  2. On button release: stop the drag and release the mouse button

My questions:

  1. Is it possible to perform a slow drag upward over a set duration in BTT?
  2. Can a BTT action initiated on press be cleanly terminated by a separate release trigger?
  3. Is there a way to offset the mouse position relative to a found image, rather than just snapping to center/corners?

I'm also fairly comfortable with Keyboard Maestro, so splitting the work between KM and BTT is fine — I just haven't been able to get the two communicating reliably, so any advice on that front would also be welcome.

Any help appreciated.