All things considered, I generally suggest pilots go down the instructing route unless it is clear they would be horrible instructors. It's a great way to solidify your own flying skills and further build a good foundation while being paid to fly the hours you need to build to get further in your career. With your experience in medicine and martial arts, you'd bring a different perspective to your students that a pilot with equal flight experience would not. Some of the best instructors I ever had, be it at flight school or the airlines, had a different career before flying, so brought more to the lesson than teaching xyz exercise. With all that said, I want to address some of your other comments. I'm not trying to "set you right," but rather provide perspective on why you may not be hearing back, from another guy who used to be involved in pilot recruiting from flight schools to airlines.
saying dual time is that less valuable than actually flying by yourself
Some recruiters do think that. Not all, but some. From their perspective what is the instructor doing? They're sitting in the airplane doing some teaching, but almost always watching someone else fly the airplane. They're wracking up PIC time while making someone else make the decisions and do all the flying. They view it in the same way as TC used to view co-pilot time. You used to only be able to credit 50% of co-pilot time to an ATPL, yet you were required to be there 100% of the time - just like an instructor. They view the pilot with 730 hours and a King Air type rating as more valuable to them than a 1,000 hour instructor, and certainly both are more valuable than a 730 hour pilot with no commercial experience.
so I figured it's worth mentioning.....they shouldn’t view this as inflating the experience, it’s highlighting the relevant experience IMO.
You have to ask whether you're highlighting experience or are you inflating your experience that is simply covered by something else. Or, in other words, are you listing a specific type rating or an aircraft that is covered by the blanket rating? If it's covered by the blanket rating, then it's irrelevant from the perspective of someone looking at your resume. That's the whole purpose of the blanket ratings: they cover all non-high performance single or multi-engined aircraft, regardless of the onboard systems. You calling out an aircraft covered by the blanket rating serves to indicate that you don't know what your license means. As a case in point, I saw one resume that read something along the lines of C150, C150A, C152, C172M, C172R, DA20, PA28-140, PA28-180, PA38-112, PA-34. To him it looked impressive that he had flown 10 different types over I think it was something like 400 hours, and I recall he said as much in the interview. But they're all covered by the blanket ratings, so from our perspective as interviewers he had flown basic single and twin training aircraft. It came across that he may be someone who liked to inflate things, and the question was raised whether this was simply youthful exuberance or was it a negative personality trait? That's not the question you want asked during a job search.
He did not get the job.
It is a fine line that you have to walk when searching for a job. At 530 hours, there is not a lot to distinguish yourself from the next pilot, but mentioning things that are included elsewhere in your license comes across negatively to many people. Keep it simple. Which leads me to this comment on this:
nearly 100 hours instrument with 10 in actual
You might have 100 hours on an IFR flight plan, but this comes across as inflating things again. I will grant you that instrument time is not well defined in Canada, so both interpretations are correct: either it's time on an IFR flight plan or actual/simulated time. But consider this: most instrument rated pilots log only 10% of their total flying time on an IFR flight plan as instrument time, unless they are actually in the soup for MUCH longer. Think about it: how often are you on an IFR flight plan but operating in VMC? A heck of a lot more than doing the same operating in wholly IMC, even if you're up in Class A airspace. When the recruiter comes to me and tells me a pilot with 530 hours has 100 hours instrument time, my gut reaction is that they may be padding their logbook. I may begin to question the rest of the stated time. As you can hopefully see, this plus the aircraft callout start to tell a story, whether you mean to or not. It's not that I doubt the accuracy of what you're saying, but when compared to 50 other candidates, yours could be seen as the odd-ball, and not in a good way.
But let's get back to your question.
should I spend the amount it cost to get the flight instructor rating and get 30-35 hours or spend the same amount renting and flying in the US and get around 150-200 hours
The difference is one is an additional qualification, the other is not. More hours puts you into the ballpark for many companies sure, but you might still lose out to an instructor, so ask yourself what is an instructor doing above all else? They're working. They have a proven track record of employment within the aviation industry. Granted, for the same upfront money you would get an additional 150-200 hours compared to the 30-35 from the flight instructor rating, but after that you're either paying for more flying or being paid to fly. If you're working as an instructor, the next 200+ hours are all paid for by the company. So when you now come to apply to an airline, instead of 730 hours total time with no commercial experience behind you, you're coming with maybe 930 to 1,200 hours total time, some of which may be a mix of instructing and charter flying. Plus, you will have interacted with people that I can call behind your back and ask how you are. While you may think it is only your printed references that are called, there is a well defined black market, if you will, of pilots calling other pilots to ask about you when you apply for a job. While I make this sound as though it is specific to aviation, it's not. My sister-in-law does the same thing with the nurses she hires. I don't care what your three references say, I want the unvarnished truth, and I'm going to get that from the gal or guy I know who ran that flight school while you worked there, or otherwise I'll get someone I know to put me in touch with that person. If you've only rented for all that time, I have no one to call and check other than your references, so of course if given the choice, I'm going to hire the person that I can check up on.
given that I barley saw flight instructor ads and the one I saw was for either class 3 and above or class 1.
That's because a Class 3 no longer needs to be directly monitored, so they're an easy hire. No one will advertise for a Class 4 because they can simply hire those from their student ranks, as rojocrv says. By the time an instructor reaches Class 2 or 1, most pilots are looking to the airlines but the flight school will start thinking they are CFI material, if they're not there already. So given there are so few of those comparatively speaking, they are in demand, hence the ads for Class 3 or above.