[Plugin: Seo by Yoast] Problems with Facebook OG

Hi there,

I’m using Seo by Yoast on my quite new blog (http://www.tuscanypaths.it) because I was told that it could solve my problems with post visualization on Facebook. Actually I successfully manage to link single post to any FB page, but everything goes wrong if I share the home page.
FB debugger tells me that
“The og:url’ property should be explicitly provided, even if a value can be inferred from other tags”
Same for ‘og:title’, ‘og:description’ and ‘og:image’.

I’ve tried to fix it following what I’ve read here and there, but actually I’m not so good with codes and eventually I got lost somewhere. All I have understood is that is a common problem, or that there probably are too many plugins.
I’m using also WP like button and Facebook feed on Twentyfourteen theme (with plugins to customize fonts and colors), but I saw that users with ‘too many og:something’ get other kind of messages from the debugger.

Could someone help me? Thanks a lot!