1. To be honest, I did Manhattan only because other people who were applying and writing the GMAT were like-minded and aimed at applying to the same school, so Manhattan was the easy choice.
2. The people I encountered who were no longer able to write the GMAT because to your point, they've maximized the 8 lifetime attempts. I don't know their personal situation or circumstances which lead to this disaster, but it happens. On a personal note, my cousin is on her 4th attempt, but I know she's just half-assing it, and not taking it seriously. I've gone as far as to persuade her NOT to pursue it anymore to save her the time, money, and disappointment.
3. Use the published score as a baseline, not as the minimum passing score. One year, it could be 710, another could be 650 (lol) and then later 740 for all we know.
[Edit]I want to emphasize the importance of the supplementary criteria as stepping stool to help elevate your application in addition to your GMAT score.
[Edit]The key here is to think big picture, and to be careful in the school you choose; This decision can change your life and future dramatically.
4. Your best bet is to speak to the university's program adviser of your school of choice. Also, LinkedIn is a good way to network with people, and also check out the university's program page as it may feature alumni who share their stories. I ended up connecting with one of the alumni at my employer who was a UofT graduate, and she was really helpful in kick starting my MBA journey, and from start to finish.
If you want to take it a step further, particularly in connecting with and learning more about programs in the US, take the opportunity and spend a week or two to meet with people to really connect with them in person, and learn from them. It's hard now given COVID-19, but maybe even a virtual meet over Skype/Google/Zoom etc. will help. Hand-written "Thank You" notes/cards go a long way.
[Edit] - Depending on the school you choose to apply to, it may require someone to vet you to ensure you are of good character and a worthy candidate for consideration, and of benefit to the school. Networking is a very important factor throughout the GMAT and application process. If you haven't started this now, I suggest you begin networking ASAP no matter what your timelines are.
Happy to answer any questions. If anything is personal, feel free to PM me directly.