This one gets asked with surprisingly regularity (or at least variations thereon)

I'd suggest looking for your answers here while you wait for someone else to reply:

/u/alexlee_sasha has a comment here about whether people really did think of the brain as unimportant in Ancient Egypt: https://www.reddit.com/r/AskHistorians/comments/krwqi0/ancient_egyptians_did_not_think_the_brain_was_an/gifvg8p/

/u/hillsonghoods has a fairly in depth answer on the perception of the brain in history: https://www.reddit.com/r/AskHistorians/comments/88759w/when_and_how_did_it_become_common_knowledge_that/

/u/hillsonghoods ALSO has an answer on the heart as the source of emotions: https://www.reddit.com/r/AskHistorians/comments/861j9a/how_did_the_idea_that_the_heart_is_the_source_of/

While this does not give you an answer to every part of your question, it should hopefully give you some of your answers while you wait.