The fact that the chosen means could never have actually killed the target does not preclude an attempt conviction.
See United States v. Dynar,  2 S.C.R. 462:
The only relevant distinction for purposes of s. 24(1) of the Criminal Code is between imaginary crimes and attempts to do the factually impossible. The criminal law of Canada recognizes no middle category called “legal impossibility”. Because Mr. Dynar attempted to do the impossible but did not attempt to commit an imaginary crime, he can only have attempted to do the “factually impossible”. For this reason, Mr. Dynar’s proposal that s. 24(1) criminalizes only attempts to do the factually impossible does not help him.
An example of a "factual impossibility" cited by the court was "impossibility due to inadequate means... For example, A tries to kill B by shooting at him from too great a distance or by administering too small a dose of poison."
That this man’s design is premised on a mistaken understanding of the facts does not make it any less his design. A mistaken belief cannot be eliminated from the description of a person’s mental state simply because it is mistaken.
Example 1: the curse
In your examples, the person who took steps to kill a person via inadequate or factually impossible means could be guilty of an attempt. Of course, this is subject to proof of the required mental state (intention to kill) beyond a reasonable doubt.
Example 2: hanging out
However, the actus reus of attempt in Canada is that the accused must have taken "some step towards the commission of the offence attempted going beyond mere acts of preparation." You haven't described anything about the person who hangs out with a militia that would constitute a step beyond a mere act of preparation.