Kadowasaki : http://www.fuji-travel-guide.com/news-item/kadowaki-tsurihashi/
http://www.fuji-travel-guide.com/news-item/jogasaki/
http://www.fuji-travel-guide.com/news-item/jogasaki-todai/

Ropeway : http://www.fuji-travel-guide.com/news-item/ropewayandoowakudani/

Irozaki : http://www.fuji-travel-guide.com/news-item/oku-irozaki-aiai-misaki/

The Izukyu 1 day pass is available, you can see the details over here : http://www.izukyu.co.jp/global_site/
Please note that you can only buy this at station where Izukyu-line run. If you come from Haneda or Narita airport, the nearest station will be Ito (伊東) station. You can buy your 1 day pass over there.

For going and enjoying all 4 of your wishlist, we recommend to plan your trip for at least 2 days.
Some of the places require you to take the bus. (Tokai bus : http://www.tokaibus.jp/)

Kadowaki Suspension Bridge : From Ito station take the bus to Jougasaki-guchi (around 30 min.) and then walk for around 10 min.
Kawazu Nanadaru Falls : Go to Kawazu station, then take the bus around 30 minutes to Kawazu Nanadaru.
Shimoda Ropeway : Go to Izukyu-shimoda station and walk about 3-4 minutes.
Irozaki Ko : Same station, Izukyu-shimoda, take the bus for about 40 minutes.

Douitashimashite~~ We hope this information help you to plan your trip to Japan 😀

My main places of interest are as follows:
IZU PENINSULA
Kawadoki Suspension Bridge
Kawazu Nanadaru Falls
Shimoda Ropeway
Irozaki ko

What is the best pass for to visit those places.

What is the length of time needed to see all of them.

Domo arigato

Warmest regards
Rachel