I know you've said that my circumstances might actually prove to be a benefit to me as all of my border crossings establish a pattern of a life in Canada but I still can't help but worry as ultimately it will boil down to who is processing my application and how they personally read my situation and want to be prepared before hand if I get asked for further information, rather than scrambling at the last minute trying to hunt down paperwork and hopeful proofs with a 60 day limit ticking down etc. I want to be prepared for the worst, whilst hoping for the best.
I am assuming your in-laws would provide a letter stating the essential facts: their ownership or rental of the residence, your occupancy with family including dates of occupancy and terms.
Documentation of address history, work history, plus an almost completely accurate travel history, makes for a strong case. If these pieces are in order, the odds of a problem range from low to very low.
This forum tends to way over-emphasize the subjective discretion of the decision-maker processing the application. IRCC processing agents are
total stranger bureaucrats. Each individual processing agent handles hundreds if not thousands of applications. If anything, the potentially problematic aspect of this is that they probably do not take the time or make the effort to assess applicants as individual persons, focused more on the data and internal IRCC criteria against which the data is evaluated. Overall, notwithstanding the anomalies reported in forums like this (not all of which are credible), the indications are that in the vast majority of cases
IRCC GETS IT, they readily identify most of those who are qualified, and identify reasonable risk-indicators triggering elevated scrutiny for some applicants, including some who are of course qualified but for the most part effectively screening out those who are short, questionable to a degree they might fail to prove qualification, or otherwise not qualified.
The OP here, for example, is at risk for falling into that
questionable-to-a-degree-they-might-fail-prove-qualification group. A member of this group may in actual fact have met the minimum physical presence requirement but not be able to prove it beyond a balance of probabilities, and thus there is a risk the application will fail.
If and when an applicant is subject to non-routine processing, that is elevated scrutiny resulting in a questionnaire like the RQ (CIT 0171) or PPQ -QAE (CIT 0205), those questionnaires offer an applicant more than ample opportunity to submit information and documentation which will effectively map a paper trail (well, more a paper/digital trail these days, just that "paper trail" is the language used in some older official decisions) of a life lived in Canada. Processing agents can read these maps. Far better than many forum participants tend to give them credit. And IRCC can usually (not always, but a rather high percentage of the time) sort the credible from the not-so-credible. Again, they get it. Really. Much more so than many whine.
That is, IRCC processing agents have "
seen-a-thing-or-two," as the television insurance advertisement starring J.K. Simmons puts it. They have the background and experience to sort these things out BASED ON THE FACTS.
On top of that, IRCC cannot unilaterally deny an application based on the conclusion the applicant has failed to prove sufficient actual presence. If the Citizenship Officer responsible for decision-making regarding the application concludes the applicant fails to prove sufficient actual presence, the Citizenship Officer must then use a File Preparation Template to make a referral to a Citizenship Judge, which template requires the Citizenship Officer to document in detail all the information relevant to assessing the applicant's qualifications with particular attention given to evidence of physical presence or evidence tending to controvert the applicant's account of physical presence. This referral is reviewed by a Citizenship Judge and the applicant is interviewed by the CJ, the applicant getting yet another opportunity to present evidence supporting his or her case, but also the opportunity to address the CJ in person. CJs, at least historically, tend to exercise more subjective discretion, taking into account the applicant's demeanor and other indicators in deciding whether the applicant is credible or lacks credibility. Many (if not most) of the cases appealed in the last two years have been appeals by the Minister in cases where the CJ simply believed the applicant is telling the truth and approved the applicant for a grant of citizenship even though IRCC's more objective assessment identified reasons to conclude the applicant has failed to prove sufficient presence.
Sure, the outcome is not always according to the
facts-known-by-god, so to say. But other than profoundly inconvenient imposition of questionnaires and such, and potentially long processing times, the process tends to lean very heavily in favour of qualified applicants. Unfair denial of citizenship appears to be rather rare.
Of course, some believe that if they were physically present 1095 or more days, to be denied citizenship for failing to sufficiently prove presence is not fair. That's a standard of fairness for religious venues not the law. And often more rooted in narcissism than reason.
Bottom-line, the vast, vast majority of qualified applicants have little or no reason to worry about how the process will go. If there is reason to worry, that tends to be rather apparent, such as in the circumstances described by the OP here.
Most of those who run into a problem should know why and should have been able to predict it, if they take off the blinders, escape the narcissistic bubble, and objectively evaluate the facts. This forum has been, historically, rife with tales of woe told by those who fail to step outside their own skin and look at the facts objectively before applying.