I'm not sure what's happening on that page when the Open Graph - jReviews plugin is enabled or why that PHP notice is showing. It looks like the Open Graph - Content plugin is still enabled as the tags on that page look to be setup pretty well.
The other thread you linked to refers to the jReviews plugin, but it seems like a different problem altogether. What you mention above isn't something we've heard of.
One thing I can definitely recommend is going to the Joomla Global Configuration area and changing the Error Reporting setting to "None". That will hide the PHP Notice which is being shown, which is the recommended configuration setting for production/live sites. PHP Notices are just that, notices for something that's not quite right and lowest on the severity of notice, warning, error. Our code shouldn't be causing the notice, granted, but in the scheme of things, it's really not an issue if the Open Graph tags are actually being setup properly.
I hope that helps get you started, but if you get the content plugin isn't doing what you need and you want the jReviews one enabled *and* the config setting above doesn't hide that message or the tags don't work properly, just let me know. We'll gladly help investigate further.
Thanks,
Alex