A few thoughts based on your profile and the questions you’ve raised:
For ISB R1, you would ideally need a valid GMAT score in hand by now. If you don’t have one yet, R2 is still very much an option, so I wouldn’t rule out applying this year.
On the sabbatical, the short answer is
yes, it could raise some questions during the application/interview process, particularly because a 6–7 month gap is longer than a typical career break. That said, it doesn’t necessarily have to be a negative if you can explain it clearly and demonstrate that you used the time productively. The fact that the initial break was due to a minor health issue that was resolved, followed by time spent preparing for CAT, gives you a reasonable narrative. I would just make sure the story is consistent across your application and interviews.
One thing I’d suggest before deciding between GMAT and CAT:
take a mock of both exams first. For GMAT, you could try a GMAT Club mock, and for CAT, take an IMS mock. See where your current baseline is stronger.
If you’re already scoring close to the range you need, I’d seriously consider taking the relevant exam within the next 1–1.5 months and getting the score locked in before you return to work. That would also give you more clarity on whether to target ISB this year or wait.
For the R1 vs R2 vs next-year question, I wouldn’t automatically assume that waiting a year is better just because you’ll have one additional year of experience. Your current 3 years in strategy consulting, along with SRCC and your academics, already gives you a credible profile. The more important question is whether you can put together a
strong application now versus a substantially stronger one next year.
Also, assuming by sabbatical you mean you have the option to resume your job, I’d ideally get the exam sorted and then return to work rather than allowing the career gap to become unnecessarily long.
Finally, given that you’re finding the process difficult to structure, getting some guidance/coaching can definitely make sense. I’d just be careful about choosing someone who can help across the entire process—
test strategy + school selection + essays/application positioning + interview preparation—rather than someone who is primarily focused on one component.