That's rough, fortunately for my own projects I'm only doing Unity on desktop, so I haven't had to go this far.
Even something simple like multiplying up and dividing down quickly adds a lot of overhead, and when running on mobiles you really need all the speed you can get.
However, complicated calculations or anything involving angles or other math functions quickly becomes more convenient when expressed as a Fix64, which is more or less a drop in replacement for float.
I would ideally use Fix64 everywhere, but given the torturous route the C# takes to be transformed into something that's executed on the client machines, my faith in the compiler's ability to generate good code for that is basically zero. I mentally treat long + long as a single instruction, but Fix64 + Fix64 as a function call.