Huh, Nbt beat F l a t l a n d e r to an RPG mod plug. How unlike him.
Yes, 4 and 5 can be answered by RPG mod, which mods the system to allow you to use things such as XP/leveling up, character selection, etc.
Also, you should learn how to script. But don't worry, if you can program you can script.
:state=1:activate=1
First colon: if statement
"state=1": if parameters (conditions)
second colon: then statement
"activate=1": then actions (actions)
After that its just a matter of learning the conditions and actions.
RPG mods adds a lot to scripting, and it requires scripting to use.
Quote: "I assume that in the FPS Store you can buy one off item instead of an entire pack of graphics for instance. That wiuld be very handy."
Yes.
Quote: "Is Dark Basic a hybrid of BASIC (or visual basic)? I use to be able to program in BASIC, but long ago. "
Yes, it is a modded version of BASIC, however it is not necessary to use FPSC. FPSC was built in DB, and there is the source code, so if you want to learn dark basic and modify the source code you can. But you do not have to.
Good luck on your project!