Hi.
It’s really hard to say and predict the number and size of textures that will work on IPhone.
Could you try to reduce all textures to max 1k res? Try to do it with like 512 to 1k texture size and check if it works. From my experience limiting resolution to MAX 1k works on IPhone. I didn’t have a situation though, where I had 200+ textures in the scene, so I am not sure if this limit to 1k will work. But for the test purpose I think it would be informative for all of us to see if that works.