In general you should simply go by the reactions of your gf/wife. If she's just enjoying the talk and getting some attention, then why go all overprotective on her?
I mean, some couples actually flirt casually, though of course they need to know the limit of their partner (the mentioned "grinding" would be a bit much to watch for most I would guess).
Girls/women can mention their bf/husband if it's getting too much... (I say that even though if it's mentioned to me then
this is my inner reaction ;P )
For most guys trying to hit on a girl, that is usually a big hint that they are wasting their time&energy(&money).
Only if the (usually drunk) guy gets grabby, your wife gets uncomfortable to handle the situation alone or even tries to "flee" to you, then you can intervene (= kthxbye).
I think the OP might have provoked the whole situation, but at least handled it quite well by not starting an actual fight / let the bouncers handle it, going by this description.
If everything fails, I'm personally ok with knocking the guy the fuck out, but still wait until the guy actually attacks you (or even her) before you do anything violent.
I'm also always hold back by the thought that random-angry-drunk-guy could carry a knife or wants to seek revenge later or has a lot of buddies around etc. etc.
There are few scenarios in which a fight is worth such risks for you and your SO (and basically depends on the location/types of people you are dealing with).