If someone tried to hide his identity, why wouldn't they be responsible for his death?
Although his clothes were most likely second hand (hence the regular removal of tags), it was a practise for spies to do that, and the second phone number found in the book did have connections to agencies, although was all of that a red herring, I don't know, but if it was, it just generates more questions imho.
Because the phone numbers (yes, there were two) in the back of the book (that the slip of paper allegedly came from) connect to Jessica Harkness and the other (not readily publicised) that had links to agencies. The "code" also was in the book, with all its own conspiratorial angles. Without that paper, what connects TSM to anything?
It's hard to pin anything down on TSM, but I'd have to ask you then, if he was seeking medical attention, what stopped him from going to a health professional? Why do you feel like he is from NZ?
I find it very strange altogether really. If an agency was involved, why even bother to allow the person to be found. You'd expect it would be easier to drop the guy over the ocean from a plane, or down a deep mine shaft, or minced up in a meat grinder and fed to pigs. By what if he actually got a heads up and was trying to get away before being caught? It appears to me that he was definitely the subject of a poisoning, so at what stage would that have happened? Jessica allegedly appeared to be taken aback by TSM's cast, so this maybe makes the whole slip of paper/book/phone number a true connection. Maybe the search of TSM actually was sloppy enough to miss the paper, and the matches.