The artifact database is storing the information used for the smart lockout policy. I don't think that's a good idea to share it at all.
Although you could change those artifact database names to accommodate, I would just go to not use SQL instead :)
WID can handle up to 30 nodes in the farm.
WID cannot handle artifact resolution which is a feature which is extremely rarely used, so not a problem.
WID cannot do Token Replay Detection, but that feature matters only if you have more than 1 claim provider trust. Most of deployments just use Active Directory as a claim provider, and in that situation, there is no Token Replay Detection anyhow.