Asakusa to Hiroshima - best route to take please

I'm sorry if this has been posted before, I'm just getting a bit confused as to the best way to do this.

We are staying at APA ASAKUSA EKIMAE (111-0043, Tokyo, Taitoku Komagata 1-12-16), which has an exit from ASAKUSA station about 2 minutes from its front door. I'm very happy with the location and access to the train station.

We will most likely be catching the Keisei Skyliner Access line from Narita Airport to Asakusa station.

We wish to travel from ASAKUSA to HIROSHIMA and this is where I'm getting confused as to the best route from ASAKUSA STATION (there seem to be two stations called ASAKUSA). I want to depart from the station closest to our hotel.

I think I want to start the JR Pass from SHINAGAWA station, but understand that there is no JR service from ASAKUSA.

1) I'd like to know what is the best / easiest way to get to SHINAGAWA from ASAKUSA.

2) If we take the 'local' train' we need to get off at SENGAKUJI station and walk to SHINAGAWA - is this correct? And if so, are the two stations connected by underground passageway?

3) When looking at HYPERDIA, SHINAGAWA doesn't show a track number for the SHINKANSEN HIKARI departure.

4) Would we be better off perhaps taking a taxi from our hotel to TOKYO JR STATION and commence the journey from there?

Sorry for so many questions, I'm just getting myself all confused and frustrated. There will be 4 of us, hopefully not too much luggage, but at least 2 medium sized suitcases and 'carry-on' sized bags.

Thank you in advance