Both the old and new locations are right under the Bang Pho station, although at different ends and different sides of the station. The new location is closer to the pier.
And I thought I was the only one who goes to Jupiter for its show. I make it a point to visit Jupiter every time I am in Bangkok. You can really see the effort put into the production. And they are always coming up with new numbers to keep things interesting.
I think B stands for Both, meaning the guy can either be top or bottom. I came to this conclusion because sometimes you see MB53 and it is unlikely for a straight guy to be exclusively bottom.
The location is indeed inconvenient. Plus, the major roads leading to it are heavily congested on weekdays. Do factor that in if you're going. I went there with Grab and was slightly late for my appointment. The experience was ok but I probably won't go back because of the hassle.
If you are getting your SIM card from 7-Eleven, make sure it is not a tourist SIM. Tourist SIM cards have some limitations, like not being able to extend the validity beyond a month or two.