My client is asking for these values to be set to the max.

I totally understand that this is somewhat dependent on the environment, however is there some sort of acceptable max on these three values?

right now I have it set to

The maximum image width/height = 2500 (he is asking for a larger value)
The maximum image size in MB, = 50 MGs

What is the suggested max values for these three settings?

It's hard to make recommendations about this, since a lot depends on what your customers server can handle. As FPD is a web application I can not recommend to increase the file size limit any further, if anything 50MB seems a bit high already (it's about the maximum my local test server can handle and that only very slowly) Canvas elements are simply not made for images that large.

Concerning the height / width I guess you could go higher, I think.