@Lovegiver, sorry for taking so long this took more effort than I expected! Here’s where I’m at with this and hopefully it will do what you require. It seems that Affix is being dropped for Bootstrap 4 and at the moment they are recommending using the HTML5 sticky property with the use of a polyfill to get it working properly in as many browsers as possible. So with this in mind I downloaded this sticky polyfill and went to work and the result can be view here and you can download a zip file containing the demo I’ve created so you can pick through it and apply it to your own project from here.
Hope this helps you achieve what you’re after. One thing to remember is that the element that has sticky will remain fixed in it position for as long as the element containing it is on the screen, e.g. if the sticky element fills its row it won’t stick!