Lana, as to your confusion:
The dispute between Pentangeli and the Rosato brothers is based on a real life dispute between the Gallo brothers and Joe Profaci, a NYC Don, in the early Sixties. Profaci promised the Gallos several territories in Brooklyn if they whacked a freelancer who was opening up gambling games in Profaci's territory and refused to pay tribute. The Gallos whacked the guy, but Profaci welshed, setting off a war between them. It came to a climax when eldest Gallo brother Larry was invited to a sit-down by the Profacis in a supposedly closed bar in Brooklyn. He was garotted to within an inch of his life, but a policeman came in, saving his life at the last moment.

Michael had been horning in on Roth's Nevada gaming interests ever since he returned from Sicily. He killed Roth's best friend, Moe Green, and by GFII, he owned or controlled three hotels and was planning to take over a fourth, and was negotiating for Roth's Havana gaming empire. In other words: there was no place in the gaming industry for Hyman Roth in Michael's plan. Roth played the wise, fatherly old man to buy time to find a way to have Michael killed. After the Tahoe plot failed, Roth went to Plan B: Lure Michael to Havana, get the $2 million from him, and have Batista's secret police assassinate Michael.

Absolutely: Tom should have known about Pentangeli's survival and his ratting out Michael. He says, "Our people with the New York detectives say he was half-dead, scared, talking out loud about how you betrayed him." But, he told that to Michael after Michael, ignorant of Pentangeli's survival, had perjured himself before the Senate subcommittee. If Tom had contacts with the NYC detectives, why wasn't he in regular touch with them? Why didn't they tip him about Pentageli right away? Tom was slippin'.