Ahhhh, Cato, Cato, Cato....You certainly picked the right user name... Anyway, as previously stated it was not Caesar that caused the "downfall" of the republic end of story. Caesar was a product of his environment. Nothing more nothing less, and he did NOTHING without precedent.
I have to quote the above. The keyword here is "personal", and should be read as "self interest".
On or around 19th March, 44BC the senate was convened by the consul Mark Anthony and a proposal was submitted that Caesar should be declared a tyrant. This proposal was welcomed by the "tyrannicides" and their supporters as it would legitimize their murder of a lawfully appointed official. However, when it was pointed out by Mark Anthony that all of Caesar's legislation, laws, and appointment would be annulled if he was so labeled, the proposal was unanimously denounced. Why? One answer. The so called tyrannicides owed their position to none other than the very legally appointed official they had murdered and they would have had to step down from their various post/positions. This is ONE example of the kind of self interest that did "destroy" the republic.
As for your bullet points, I welcome the starting of a discussion pertaining to these.