Nice job, he4rty!
If you saved xcf version of your work with D-map, I would recommend trying one more thing. Instead of displacing in X-coordinate, try Y-displacement with the same workflow and see how it works out. Instead of going east-west the fg object (man in this case) will move south-north, or should I say, the hypothetical observer would move up, over and down. I would love to see the final animation!!!
Don't know if mine is maybe a bit slow, thats about the only thing missing from the tutorial is a guide to what frame rate should be used.
I set mine to the default 100, then changed to 140 ms, because it was a little bit faster than I'd expected. But in GIMP it's easy to change frame delays using scripts, there's actually quite few of them out there.