1) you may want to set up a small workbench partition with a minimum install. Resource hungry games/demo's can be ran from that partition.
Problem is the chip ram tools you use 'give it back' from whats taken that RAM after boot, so it ends up in seperate chunks (not one contiguous one). E.G: you have 1700K +100K, rather than the 1800k you think you have.
run 'avail' from a shell, and look in the 'largest' column to see how much contigous chip you have. Try to free up more ram by typing 'avail flush' from a shell window.
2)disable each patch in turn in your startup-sequence by placing a ';' in front of it's line. this will pinpoint the problem. Only install patch's one at a tine with each boot. Always read the docs to make sure they work with each other!
3) don't know mate, check on aminet, or search the old magazines
http://amr.abime.net/*edit* maybe this one:
http://aminet.net/package/misc/emu/ABeebalso,check this article you can also use mac classic emulators (you will need a beefy amiga for Beeb emulation):
http://www.simon.mooli.org.uk/AF/6.html4)only if you start to run out

I did on 3d rendering so used it. VMM was the program I think.
5) can't help there.
6) SDL requires a graphics card, as far as I know.
7)out of my depth here
