"No hay tarea difícil, sino hombres incapaces" - Ernesto "Che" Guevara [1]
That would translate (i think, correct my english if i'm wrong) to: "There is no difficult task, but incapable men"
Guevarra was politically naive and made many awful decisions w/r/t ideals, strategy, and tactics, with in some cases disastrous results. I think heroizing or canonizing him is a poor choice. But calling him a “mass murderer” robs that label of meaning. By any standard which you might consider him a mass murderer, most US presidents of the past 80 years would equally qualify.
With regards to all three of your claims, this seems like a fairly reasonable analysis: https://www.reddit.com/r/AskHistorians/comments/1lt4rb/was_i...