Session / Cache Issues - Time Sensitive!

Joomla Version: 3.5.1 (Can't update to 3.6.4 due to the below issues)
CB Version: 2.0.15 (Update isn't showing up as an option)
Akeeba Version: 5.2.5 (Read where this could be the problem...?)

Issues:
When I log in sometimes (not every time) as an administrator, I get the following error
["The most recent request was denied because it contained an invalid security token. Please refresh the page and try again."].

Additionally, when using the CB Login page for front-end users, they get the following message and can't log in
["Session expired or cookies are not enabled in your browser. Please press "reload page" in your browser, and enable cookies in your browser. Please refresh/reload page before filling-in."]

When I edit anything on the site (even articles), it shows to save successfully on the back-end, but nothing changes on the front-end. Seems like a caching issue, but I don't know where it could be coming from.

Doesn't sound like your issue is specifically with CB. If you've caching problems then turn off caching within Joomla. Page caching is typically the culprit of a lot of issues like this as it'll cache the entire page buffer causing out of date information to be output.

What settings are available besides the one shown?

That's enough to turn off Joomla cache. Check within System > Clear Cache and see if there's any cache stored. Some templates or extensions have their own caching functionality. Try clearing the cache if there is any to see if your issue persists. If your issue does persist it maybe a caching problem coming from your server, but probably not likely.