You're analysis is very similar to one I gave a couple years ago. He had a wide range of knowledge and skills. Maybe "death wish" was a misnomer...I didn't mean that he literally wanted to die...but He seemed to tske self sacrifice to an extreme. And he started out that way. Whereas Hoshi began as a more timid, fearful, uncertain person.I think that Malcolm was willing to die for his Captain, crewmates or ship as Chief of Security but as for a 'death wish' I don't think so. The only reason would be that he didn't want to live alone the rest of his life. He also had a fear of drowning which is why he joined StarFleet so why would he want to die? If he had not been there on Enterprise, they wouldn't have had the "Reed Alert" or the stun added to the phasers. He's always been ready to help and even helped Tucker many times which shows HE could've become an engineer too. Makes you wonder what he did do after they returned to Earth permanently.
It always confuses me as to why Malcolm was only a lieutenant. It seemed to me he should've been at least a lieutenant commander .