The '?' was pronounced like the 'ey' in 'hey'
It's rather a long e (IPA: [e:])
ae and oe are both pronounced that way.
C is always pronouned [k] (Circus = [kirkus]) and qu is pronouned [kv] (five = quinque [kvinkve])
So it's rather just the "e" in "hey" rather than "ey" which brings an extra [i] which does not belong there.
IIRC there is no certainity for the origin of "Caesar". The most likely theory is that he just happened to be born with the name like so many other people on earth are just born with their names.
Pronouncing latin is quite difficult for an English speaker, I've observed. There are unnecessary "ah"s and "wah"s all over the place. "Ave" is a short, sharp and official greeting. The one with a more loose pronunciation would be "Sal[-ve][-te]" which is the more familiar greeting.