First of all, do you actually own the copyright to the photos? You describe yourself as a second shooter on the job and if the videographer actually hired you under a "work for hire" arrangement, by default the videographer owns the copyright and can do with the images whatever he wants.
On the other hand, it sounds as if you were the still photographer and he was the videobrapher at the wedding, so you each might have contributed your portion to the overall job and shared the rewards. You might still own the copyright, but I would sure have wanted to have it all spelled out in writing and signed by both parties before agreeing to do the shoot.
As to the third party now using your images... Wow! The word "despicable" doesn't quite cover it.
I can't think of anything much worse than misrepresenting yourself by showing potential clients someone else's photos and pretending they're your own. Unless he's disclaiming the photos. And I really can't imagine someone saying "Now, these are the type of photos I'll take for you at your blessed event. Actually these photos were taken by someone else, but I don't have any work of my own to show you because I've never shot a wedding before" or "My own stuff just isn't good enough to show you, so I'm showing you someone elses'."
If, as I suspect, he's representing your photos as his own, he is literally lying to every potential client he pitches and I'd have no sympathy or qualms about calling him on the carpet about it in front of clients and other photographers. B&Gs need to know that he's a fraud, before they contract with him to handle their wedding. Other photogs need to know he can't be trusted.
If it were me and I knew I owned the copyright to the images, I'd have been sending a Cease and Desist letter drafted by an attorney... Registered mail requiring a signature as proof of receipt... Not emails.
I'd also demand all copies of the images be returned to me immediately, from both the videographer "friend" and the third party now using and passing them off as his own.
If you don't have a lawyer, check if there is a "Lawyers for the Arts" office in your area. They usually offer free consultation and specialize in intellectual property rights infringements. You might start at:
http://www.calawyersforthearts.org/
There's no flattery going on... Just plain theft. And following that, fraud. You are being waaayyyy too nice.
And, yes, if you still own the copyright to your images and your videographer "friend" is giving copies of them away to other people - or worse, selling them to the third party - then you have a major problem with him, too. He should know better than giving away someone else's work and furthering the third party's fraud. Another Cease and Desist letter is called for.
Finally, did the B&G and everyone else in pictured in your photos sign a model release so that the photos can be used for commercial purposes? You might be on pretty safe legal footing putting those images in a portfolio of your own work (that's considered editorial usage, no release is req'd tho it's still a good idea to have one). But anyone else using the photos for promotion and marketing is putting you, your videographer friend and themselves at risk doing so without signed model releases.
But, hey, what do I know? I ain't a lawyer and you really should be talking with one.