Okay... first let me note:
The server is already very much overloaded.
That said, SMF shouldn't be so slow to load even withstanding that. However, your load averages are "11.28, 9.85, 5.62" which is horribly high, they should be under 2.0. Memory usage is, luckily, fine... except MySQL clearly cannot keep up with the number of (vBulletin, mind you) queries being sent to it - as I type it has 39 concurrently running processes, which shouldn't be. This is, mind you, under the same account you have installed SMF under - it could be worse server wide.
However, your server is only getting about 6 queries per second, which isn't very much.
As for CPU usage, httpd is using well over 100% which is clearly a bad thing. Still, if that software is able to continue on the same server reason dictates that Apache must be free enough to do other things. Especially as the status script loads fine.
From Grudge's test data it looks like making the connection to MySQL alone - which is one line - takes half a second, which is almost unforgivable.
From this data, it is painfully clear that my suggestions about overall improvements to the server (bytecode caching, MySQL version within the last two major stable releases, etc.) would be of significant and important effect (whether you continue using vBulletin or not.)
-[Unknown]