Did Tony violate Omerta by coming to Melfi?
He told her a lot over the years, for example;
-He mentioned how he had a guy beating up people in a whorehouse while she was on the phone with him
-He talked openly about how his father (albeit deceased) had a crew, and how his father never got as high up as him.
-He mentioned Pussy Bompensiero, by name, and referred to him as "stone gangster" (before he knew Puss was a rat)
-He detailed to Melfi his plan to use Christopher as his buffer to the rest of the family. He basically plainly spelled it out for her there that he was a Mafia boss (saying he knew a guy in his position who lived in Florida until he was 81 because he gave orders only through his son).

There's other things I'm sure others would remember. Also, he dimed the two Arabic guys to the Feds, giving the Feds their phone numbers and names and telling them info about them. Even though they were just Associates of the family, wouldn't it be considered snitching?

There were other reasons for Ralphies death but it's what finally tipped him over the edge
-Unofficially taking over the Aprile crew without permission
-Ralphie killed Tracce
-Gave Gigi Cestone stress
-Tried to bring Jackie Aprile Jr up the family and possibly Tony had some suspition that Ralphie had something to do with the robbing of the card game (not intentionally of cource)
-Possible hold back of profits from the Esplanade I mean look at that house and car surely that cost over 1 million