Someone had this interpretation in the comments section on youtube: "It's the angel of death looking at Tony. I think the suggestion is that the train of events that will lead to Tony's death has now been set in motion."

Makes perfect sense. In this episode Tony is feuding with Carmine and Johnny, and so decides to call on Little Carmine to help settle things. This is the inciting incident that will lead to the war with New York in season 7 and Tony's death in the diner, whether at the hands of the Lupertazzis or his own fed up family (Patsy/Paulie?). Tony elevates Little Carmine in the latter's eyes, and puts the idea in LC's head that he could be more than just a Capo in Florida that fixes wet tee-shirt contests and run a film company in his sub-species. When Carmine Senior dies, Little Carmine goes to war with Johnny for the boss title.

If Tony hadn't asked Little Carmine to run interference, Johnny would have easily slipped into the role of boss. No inter-family war means Tony B isn't hired for outside help. He doesn't clip Billy Leotardo, Phil isn't bloodthirsty for revenge, and Johnny doesn't have to placate Phil by making him the Acting Boss when Johnny goes to prison. Angelo probably gets that title and Phil remains a Capo. Phil still gets pissed when Vito is outed but he and Tony work together in taking him out and that's that.

Meanwhile Tony B gets made between season 5 and 6 and probably takes over the Aprile crew from Vito and eventually is the one who's made Underboss instead of Bobby in season 7.

Regarding the dream, I think Tony briefly died just a few seconds and was taken on a "test drive" to Purgatory/Hell. He jolts awake just as he takes his first step into the house (or Hell), out of breath, sweaty, clutching his heart, and confused similar to "who am i, where am i going?" Still sort of between worlds when he goes to the bathroom with the red light, then finally comes out of it when he opens the windows to the bright land of the living. He's back at the house with the specter when he's shot by Junior.

And if you look closely in the final scene, when the Members Only guy is walking to the bathroom, there's a picture on the wall of what appears to be the house at Tony's three o'clock.