16 days with 2 kids.

Hello!

We'll travel from Hungary to Japan next April. We'll make a big tour starting at Haneda Airport, then Hiroshima, Osaka, Tokyo and a lot of other places. So JR Pass seems to be a good choice for us. I spent the last week to figure out the details, mainly regarding the railways and I found a lot of things which contradict each other. These are my questions, please help me out.

1. Is Tokyo Monorail free with JR Pass? I found conflicting information on the internet about this.
2. We would travel to Hiroshima from Tokyo. We don't want to take the Nozomi shinkansen as the JR Pass is not valid. Which station in Tokyo can we board and which other shinkansen than Nozomi available? (I arrive at Haneda Airport.)
3. Do we have to transfer to another train to Hiroshima or is it enough to get on in Tokyo and get off in Hiroshima?
4. Where can I register for a seat on the shinkansen? Online (outside of Japan) or only in Japan at train stations?
5. How do we know which seats are occupied and which are not occupied on the shinkansen? (I'm asking in case we don't reserve a seat in advance.)
6. When we validate our JR Pass at the airport, can we pre-book our seats on the shinkansen to/from all the planned locations of my trip at the same time? My 16-day trip has the exact schedule of when we will be in which city.

Thanks in advance for the answers!

Regards, G.