Had very similar problems on the X8 which is same phone set up. There are no calendar settings to speak of on the stock app. Someone came up with a solution but I have yet to see if it works properly.

Go to your Google calendar on line and choose Settings top right of screen, then Calendar Settings, then choose Calendars and click on Notifications and then Event Reminders and set to No Reminders. The theory is that it won't set up reminders for every event and therefore you won't get rogue notifications going off. The only problem is that this will only affect new events not those already in your calendar.

I use Jorte calendar app on both my phones, much prefer it to the stock one. It's a free one on the market so maybe worth a look at. Got much more customisation as well.