Stopping within horizontal scroll

Hi all,
I’m hoping somebody can help me out with a horizontal scroll question.
I’ve got a site that is basically separated into full viewport slides. It starts off with a couple of standard vertical scroll slides, then goes into a number of horizontal scroll slides and finishes with vertical again.
That all works fine.
Eventually these slides are going to be filled with content and some are going to be animated upon entering the view and others are going to have some content that will be animated with the user scrolling.
That means that some slides are going to have to stay on screen while the user is scrolling, and in turn activating an animation, and when the animation is over then the horizontal scroll continues to the next slide which may or may not need to be held again for another animation.
Does anybody have any suggestions on how I can hold the horizontal scroll on certain slides?

I thank you all for your time and any suggestions.

Here’s a read only link to the test site.