3. The only way to add a SID to your Amiga is to install a Catweasel Mk. 3 and stuff a SID on that and as for where to find SIDs check this
thread. Or pick up a C64 somewhere in your neighbourhood and rip it out of that.
4.
Clickety-click. I have no idea what the guy is doing nowadays.
5.
How about this, can actually be bought
here :-). I know there's also a Zorro 3 card which was exclusively a memory board taking 72 pin SIMMs, IIRC made by phase5. But I can't seem to find it again on the hardware databases :-?.
7. If you do a search on a.org you'll find that somebody started a Telnet BBS recently again. I'm sure there's still quite a few of those about. But actual phone line BBS'es? I doubt it.