Ferry from Osaka to Tokushima?

My husband and I are planning to travel Shikoku early in December. Can't decide whether to leave from Osaka or Wakayama by ferry. Which would be best? Can we travel from Osaka to Tokushima by ferry?Also would the weather be too cold in this time? Also is it best to hire a car? We will have about 7 days to tour the island. What would be a good itinery? Any tips for accommadation. Also do you know good deals for accommodation in Wakayama. We land in Kansai at 5.30 pm and will be quite tired. Should we stay at the airport hotels and then travel the next day. What would you recommend? So many questions... sorry.

Nankai Limited Express "Southen" (from Namba, Osaka) and Nankai express/local (from KIX, one trasfer at Izumisano station) takes you to Wakayama Port, where you can take a ferry (Nankai Ferry) to Tokushima Port.
Timetable (Japanese)
http://www.nankai-ferry.co.jp/timetable/index.html
*from the very left, departure at Namba, departure at KIX, arrival at Wakayama port, ferry departure at Wakayama port and arrival at Tokushima port.

Another option is highway bus from KIX to Tokushima station (3hrs).
Timetable (Japanese)
http://www.tokubus.co.jp/topics/20071101/kanku.htm

Can we travel from Osaka to Tokushima by ferry?

No, there is no direct ferry. You have to go via Wakayama. The direct bus is the fastest and cheapest solution, as outlined by JLady.

Also would the weather be too cold in this time?

No, if you bring suitable clothes, it is never too cold.

Also is it best to hire a car?

It depends where you plan to go. If you plan to visit just the cities, you can easily do it without a rental car. But if you plan to explore the countryside, a rental car is recommended:
http://www.japan-guide.com/e/e2024.html