If Malcolm isn't killed off by the end of this season, then the producers have literally gone past the "overkill" point.
Malcolm, as a character, has already stayed longer than he should have as a main character for this show. I get that John Barrowman is a great actor and fun guy to be around, but there's no reason why he should still be involved after this season, especially if his actions leads to the death of Oliver' son or another close companion.
And if Oliver goes on about how he still can't kill Malcolm after losing yet another person due to Malcolm's actions, then Oliver has officially become Malcolm's *****.