Was Caesar over ambitious

Caesar was indeed ambitious. If he was ambitious, why did he refuse the crown offered to him by Mark Anthony? It is all part of his plan. If it looks like Caesar does not want to be emperor, the people will want him more. He was already dictator Euterpe. The crown was just a formality.

One of the indications of his desire for power is to look at how he refers to himself in the first person. He elevates himself above everybody. He doesn't say "I will go forth". he says, "Caesar shall forth".

In his desire for power, he attends the Senate against all omens warning him not to go.

Did he need to be stopped? If Roman was to continue as a Republic, yes. Was the the way to stop him to kill him? Assassination is never a good solution.