The T30 is a desireable classic, and a far better sailor IMHO than the Paceship or Bristol. The T30 is built like a tank, I'd consider it unlikely the keel is sperating unless the lead has obvious damage from abuse. Do you really mean that it is loose, or has some filler come out of the keel/hull joint, creating the apprearance of a crack? This condition is quite common on fin keel boats...Not to say this boat can't be a problem, just not likely, and worth getting a professional opinion on. The T30 is a sweetheart of a sailboat.
Certified...in several regards...