Travelling from Tokyo to Mt. Fuji (Gotemba) to Osaka

Hi,

Im staying in Minato City.
Calculating my trip from Tokyo to Osaka; this trip is ~3 hours 30min.
My plan was to stop on the way to Osaka in Gotemba near Mt. Fuji.
So now the Trip would be Tokyo (Shinagawa Station) to Gotemba; this trip is ~ 1 hour 30min
Then from Gotemba to Osaka; this trip is ~ 4 hours
In total: 5 hours 30 min

I have a couple questions that I need help with:

1. Why is Gotemba to Osaka 4 hours when Tokyo to Osaka is 3.5 hours? Mt. Fuji is in between both so i'd thought the time would be half of that.

2. What is the fastest route I can plan from Tokyo (any station near Minato City) to Gotemba Station to Osaka Station?

3. Does the trip use the JR Pass?

Any help is appreciated heaps!!!