Your approach is basically the correct one, try to keep your buffer, if it comes to it (emergency happens), try to return while still in compliance, if you go out of compliance, try to keep it the non-compliance small, and be prepared to stay in Canada until back in compliance.
While no-one can guarantee, they overall do not try to 'catch someone out' for relatively small non-compliance. No, I can't put a number on 'relatively small.' But with relatively high probability we can probable say that even if examined, with clear evidence you are residing in Canada (which your travel record alone mostly shows) and some plausible reason why you had to leave (the family emergency), no, they probably would not start removal proceedings. They might warn you, they might not, they might put a note on your file (pushing examinations to other officers if you then leave and stay abroad for much longer).
BUT: on a gut basis your bigger risk is perhaps to your livelihood if your work requires you to travel so frequently. At some point, you may (and probably will) end up without a valid PR card for some period of time, which might be longer if you have to re-apply when you are only just in compliance (call it 'cutting it close.') Does not having a valid PR card cause employment and travel problems? Does your family emergency come at a time when you don't yet have the pR card rnewed?
Or you get a note to file that causes you to be re-examined frequently, and then one day you get a CBSA officer who decides they don't like the pattern (even if the overall non-compliance isn't that large) and you end up having to appeal, etc.
Or - and this is perhaps the more common problematic scenario here - another emergency or family issue comes up after that, you're abroad without a PR card (and possibly can't travel back via land border), this time the family issue keeps you out of Canada even longer, and next you're much more seriously out of compliance and finding it hard to get back (causing employment issues in Canada, etc). The risk of issues on examination goes up with the degree of non-compliance.
I don't mean to 'catastrophize' this by coming up with endless scenarios, one worse than the next. I doubt you'll have such problems, precisely because you're taking it seriously now, and paying attention to it. Overall I think you're probably in good shape unless something very problematic comes up. Your buffer is decent but it's not that much for the ~two years remaining before you've got that solid 730 recent days.
