use the theme without using event platform?

Which scenarios do you have in mind?
Doing so would mostly be reconfiguring the SDC components to map whichever fields they provide the data.
So it's possible, but it's more challenging than an out-of-the-box experience as the event_platform integration provides.

I needed a quick off the shelf theme, client liked the layout/colors vs all the others on drupal.org. I was able to edit the right pieces to get it to work for me (header/footer/nav).

Nice, that's great to hear. We might be able to add some docs about it to make it easier for others who might try to do the same.

One other possibility would be to make more general-purpose version of this theme, and then make this project a more opinionated subtheme of that. I don't really have the bandwidth to take that on at the moment, however.