Mortality of the self is not a big deal, at least if the illusion of ego was already overcome. On the matter there is for example Epicurus classic thought that self death is not a concern as while alive self won’t experiment it’s own death, and once dead there is no longer any self to observe death. That one requires accepting there is no "afterlife" for the self.

Thus, only death of others is a relevant topic of concern, but taking care of them while they are alive is certainly far more important.

Impermanence of everything "only" applies to contingent matters. So statements like "everything (that happens through some contingency) is impermanent" always match some absolute truth. So the apparent contradiction that "if everything is impermanent was true, so should be impermanence and then not everything would be impermanent", is only indeed apparent.