Think you have asked these questions before and I have replied. Anyway, here goes again

Conventional flights 4 a day from Athens to Corfu. Bus/ferry about 4 or 5 a day. Seaplane is based in Corfu and currently flies to Patra, Levkas and Paxos.

Allow 6/7 days by yacht through the Corinth Canal. Can be done in less but not in holiday mode. Couple of stops in Gulfs of Corinth and Patra. I stopped at Kiato near the western end of the canal (rather grim) and Mesolongi (interesting). Other interesting stops mainly on the North Coast.

Once you get into the Southern Ionian you are spoilt for choice, but most popular if going north to Corfu are Nidri or Levkas town. Can do Levkas to Corfu in a day, but best to split it in two and stop in Paxos. You will have time for two more overnights which could be ither in the Southern Ionian or mainland north of Preveza.

Invest in Rod Heikells Greek Waters Pilot which will answer most of your questions and many more. Also there is a a guy called Jim who posts regularly on here and the Liveaboard forum who has an excellent website of detailed information.

Enjoy