Hi Cliff,
Thank you for your response. Unfortunately, we cant upgrade WordPress to 4.3.1 at this time. We have several production sites running on our WP platform right now so that has to be well planned. We do have plans to upgrade to the latest version of WP but that probably wont be by the end of this year.
As for upgrading the Events Calendar PRO plugin, WP is showing that there is no upgrade available for that plugin and just browsing your site I didnt see mention of an update for it. We definitely would be interested in upgrading this plugin, how would we go about doing that?