About Carmela, during the series you could see she was in love with Furio, and he loves her too, and I doubt if Tony was whacked, someone would have thought of what his wife would do.
The character of Johnny Sack IMO is inspired by John Gotti, both because he wanted to kill his boss, either because it's being criticized for be trigger happy,because it has been a stand up guy to the end, and because he died of cancer in prison.

For the murder of the cop that allegedly killed Dickie Moltisanti, you could say that since the rules of the Mafia, forbid to kill cops, Tony waited until the cop retired, but I think it's an excuse to tie more Christopher to him.

Tony during the series, always complained that the captains didn't earn enough money, now agree that Tony is against drugs, as he told to Pussy in 1995, but since he had relations with the Camorra, because he hasn't try to create a zip crew, only for the drug trafficking, Tony has never seriously attempted to expand the family business.
In the 2004 about Tony Blundetto and Fech LaManna, rather than rewarding the cousin for the 20 years in prison without flip.
He didn't made him,maybe under Fech as captain.

In this way would have more two capos, and would have earned more money, but it's just my opinion.