This reply is actually more so for anyone else who has a similar question.

A day after i thought i tweaked the performance all my sites went down with XOOPS saying it couldnt connect to the DB. tried to connect to DB via phpmyadmin, no love with a error of too many connections. I called up the provider (they are one of those huge wait on hold for 5 minutes companies)... i speak with a rep and find out theres an on going problem with the DB servers which for the past few days was giving some users heck.

Everything is back to normal and ive added several blocks to my other sites.

Again thank you to everyone who responded :) just wanted to bring some closure to this topic.

On the same note as this topic, what if I want only the USER related tables to be shared across multiple sites but everything else have it's own db? Is this possible with XOOPS?