Flashart

Some say that Session Drummer is part of HS7 but I couldn't find it... 

Session Drummer was included with version 6 of Home Studio XL, but I believe that version 7 has Studio Instuments Drums instead.

I think I used a drum map correctly last night. ie The correct map name for the correct name soft synth. The drums appeared to be in the correct places but what I found unusual was that most of the action takes place in say, numbers 38 to 58 but then there would be a big gap and one thing at 91 then another at 98 etc. I get that these things might correspond to a certain pitch, but is there anyway of knowing how many available sounds there are without manual scrolling through the numbers?

Are you opening the PRV(Piano Roll View)?
This is where the map information is most useful.
Below, I have two views of the same track, showing slightly different information.
Both have the PRV showing to the right.
The first shows the normal track view with a regular MIDI clip at center.
The second shows the inline PRV at center. I don't really like the inline PRV, because it is somewhat limited.
Also, coming back to your original export question, notice that in the second view, the synth audio output has been set to my master bus. This is beneficial for overall control of your projects, as well as making your exports go smoothly.
Both of these views are in the SHS7/MC5 format, and should be similar to what you see.
Are you seeing something different?
Also, what synth and map are you using?