Business school chances if I quit IB analyst role after undergrad

Currently a matter of months into my first year at a shitty lmm IB and its awful. I am close to getting an FP&A offer after some great interviews, and have a question on my mind.

if I leave IB after only a few months and then stay in FP&A (its a very small company), what are my options later on, such as getting an MBA?

what are all the other career paths I would even be eligible for coming out of an m7, if i would even be eligible for M7 (i have a high gpa from a t15 undergrad)?

i want to take a risk and jump to this small start up and also have the time to focus on some personal matters, but i dont know if I am setting myself up to never earn my current salary (110k) again until i am 30. Thats the only thing holding me back - the chance that ill instantly regret quitting IB and go back to being an unhireable candidate with no experience if this start up goes under