Short answers, pulled from the story.
The Tito-Stalin split officially began on the 27th of March 1948 when Stalin sent his first letter addressed directly to Tito and Kardelj. This letter denounced them along with Milovan Đilas, Svetozar Vukmanović, Boris Kidrič, and Aleksandar Ranković as dubious Marxists.
The Cominform published its Resolution on the KPJ on the 28th of June 1948 exposing the conflict publicly and criticizing the Communist Party of Yugoslavia for anti-Sovietism and ideological errors. Thousands of people were imprisoned, killed, or exiled following this expulsion from the international organization including up to twenty percent of the KPJ membership who supported Stalin instead of Tito.
Yugoslavia faced significant economic difficulties after losing trade with the Soviet Union and Eastern Bloc countries which led Secretary of State Dean Acheson to recognize that providing aid to Tito was in United States interest. The U.S. decided to provide economic assistance in February 1949 under specific conditions to help overcome poor harvests experienced during 1948, 1949, and 1950 despite almost no economic growth before 1952.
Hungarian Major General Béla Király claimed plans existed for military intervention after defecting to the United States in 1956 but later research by historian László Ritter disputed these claims based on absence of archival material documenting such plans. In immediate aftermath of split at least one failed attempt occurred at a Yugoslav military coup supported by Soviets involving Colonel General Arso Jovanović and Major General Petričević.
Stalin summoned Yugoslav representatives to Moscow on the 10th of February 1948 for critical discussions where he demanded an end to the insurrection in Greece and an immediate federation consisting of Bulgaria and Yugoslavia. The KPJ politburo met secretly on the 19th of February and decided against any federation with Bulgaria interpreting it as a Trojan horse tactic.