I'd Like an MD5 Checksum computed and stored for all files in my share folder.

I'd like files in my search list which match the checksum of an already existing file in my share to be filtered out or into a different list. 1 prefer a different list just in case.

I'd like to IP mask block people from downloading files from me.

I'd like to filter out any files from a given IP mask.

I'd like to file certain files at not being uploadable without having to remove them from the share folder.

LimeWire and the other gnutella servents decided to use SHA-1 instead.
That's not very useful, since the cases, where to hashes are the same, are rather rare and the effect of this feature would be noticeable.

You can. Options->Filters->Hosts

You can. Options->Filters->Hosts
Why would you want to do that? But anyway:
foo@bar: ~/Shared> chmod 000 file
should work.