My opponent has Westvale Abbey and 6 creatures out. Assume I am impetuous and have cast Grip of Desolation targetting the abbey and one of my opponent's creatures rather than wait for them to flip abbey first. My opponent responds to grip by transforming abbey.

There are two situations i wish to know the result for:
1)my opponent sacrificed the creature i was targetting with grip to the abbey, leaving grip's only target as Ormendahl.
2)my opponent did not sacrifice the creature i targetted with abbey, leaving grip's targets as both that creature and the newly transformed Ormendahl.

targets are separate. you targeted Abbey as "target land" so if it stops being a land then it no longer qualifies as a viable target. in situation 1, that means your spell fizzles because it has no legal target. in situation 2, Ormendahl is still an illegal target, but the creature you targeted is fine, so the spell resolves and does as much as it can, destroying the object it can still legally target.

I don't read cards, I just assume they do what I expect them to.

Thanks much!