I completely agree. Keep your boundaries, like the FB thing, but it's only a matter of time before he screws up. If anyone other than family gave me their opinion about how to raise my S, there'd be minimum a dirty look, openly. Worst case scenario, it would get ugly verbally.
And the ILY's....I'd stop too. It's pressure.
The compliments....if it's geniune and appropriate, like she has a new dress, new hair cut, I say OK. But to compliment to compliment her looks like you're trying to compete with this guy and you have to take the attitude that you're better than him and you're just patiently waiting for her to figure out what you already know.