Look--there's risk EVERYWHERE.
You've already pointed out the hazards of developing a marketing strategy dependent on a single platform.
You've also noticed that you need to set your price to buffer against rising short and medium term costs.
Startups should test and scale with whatever promotional media is resulting in increasing sales. Do more of what is working.
No one can give you a magic ticket or golden path to success. There are no guarantees. Anyone who tells you that is lying...even if they aren't consciously aware of it.
Nobody can guarantee YOUR product or service will take off on a platform they have experience with.
Nobody can guarantee YOUR ads will ever be approved and see the light of day on a platform they have experience with.
Nobody can guarantee copy that worked with their niche on the platform they're familiar with will work for you.
Test, and find out.
Business is made up of choices and risk. You do your analysis, pick your best likelihood of success, and set your course. Sometimes it works out and sometimes it doesn't. What matters more is how you handle that feedback.