Hi,
You can probably go higher with the number of poly, but just for this assembly, you can definitely get it for less with some simple low poly designs ( it depends the level of quality you want to achieve of course). It's missing the front view to understand the shape of the pedal itself and the depth of elements.
Keep model as fbx yes, it will guarantee control on mac and windows. You can import max files, but then you loose settings fine tuning on mac.
Texturing is always done by UV. no other way. If you mean having to manipulate the UV in your modeling software to achieve the desire result, than yes, and it's true for any kind of texture based modeling, not just for iOS.
Each moving parts needs to be individual mesh yes. You could get away with submeshes and clever tricks, but if you are starting up with all this, best is to stick with one model or group of models per animated part.
You are better off having the pedals and all its components animated in max. You can do it all in unity, but you need some advanced skills ( for example the linkage 38 will give you headache if you want to animate it realisticly). what you would do is make a simplified version of the pedal and the head that would be physically defines in unity and then map the rotation of the physics pedals with your animation.
Don't know what you are trying to hit, but if it's the drum itself, you can get away with not even care about the head and simply mock it up because you know when it hits and you just need the force applied to know how loud the kick will be.
Of course, as a school project, using joints would be very interesting. I have done something similar ( a complex rig of joints) with an excavator simulation, totally off topic at first glance, but very much identical to script and rig. basically several pivot joints acting/reacting together to move a mechanical assembly. You could even realisticly model the spring using physics and adjust the tension of it and have the pedal properly react to the spring tension :)
Have fun with this project :)
Bye,
Jean