How can I remove the page heading?

Have you tried the Disable Elements section?

I wonder which element is creating that white space? A link to the page would definitely help :)

I disabled: Header, Page Header, Content title

http://screencast.com/t/rgV0n42rKJb

Test Site - http://pastorschaller.com/site3/page4-2/

Could it be caused by Elementor page builder plugin?

Ah, it's the content padding.

On that one page, add this CSS:

.one-container .site-content {
    padding: 0;
}

You can add it to that page only using Simple CSS: https://en-ca.wordpress.org/plugins/simple-css/

Tom. It works perfectly, thank you!
http://pastorschaller.com/site3/page-5/

Why is the padding there? Would you consider adding a theme option to remove the padding when the 'Content Title' is disabled?

The padding you see there is the content padding option. I may add an option to remove padding in the "Page Header Integration" metabox if "Full Width Content" isn't selected (as that removes the padding anyways).

Thanks!