Hi, Need an itinerary check/advice

Plan
1) 7:22am Catch Hikari Shinkansen from Shin-Osaka Station to Fukuyama Station
2) 8:00am Pick-up reserved car
3) Drive along Shimanami Kaido to Shimanami Dolphin Farm (Aim to arrive by 9:40am for start of session)
4) Continue driving along the Shimanami Kaido to Omishima Sakari Port 盛発
5) 11:25am Catch the Omishima Ferry to Okunoshima Island
6) 12:45pm Catch the Omishima Ferry to Tadanoumi Port
7) Drive using tollway (E2) to Hiroshima, return car, and head to Peace Memorial Park
(Estimated arrival time assuming no delays/getting lost: 430pm)

Questions to ask:
a) I am wondering if this plan is doable?
b) How long does pre-checks taking when collecting a reserved car? (Rushing to get to the Dolphin Farm on time)
c) Regarding catching the ferry departing from the Omishima Sakari Port, is this route risky to try to get to Rabbit Island from here instead of Tadanoumi Port?
d) I know one cannot drive on Rabbit Island, but anxious and worried that we will be told that we cannot park at the port on Rabbit Island?
e) Is visiting Shukkeien Garden at about 5pm too dark/too late to see anything? (Going in November)

Thank you