Hi Jonathan,
You’re going to have to modify and play around with the CSS to get this just right in your theme. I would suggest overriding the events.css stylesheet by making a copy of it in an ‘events’ folder within your theme directory and then tweaking the .tribe-events-calendar-buttons (or .upcoming .tribe-events-calendar-buttons to be more specific) class.
For example, if you set a width for that class that will at least make it so the buttons aren’t stacked but you’ll still need to modify it some more to get it to look just right.
I hope that help but let us know if you need anything else.
Regards,
Jonah