Mount it higher up just under the eaves of the roof?

I would think so. A lot of the pumps claim to be weather resistant, but keeping something out of the weather usually is better for longevity for most items. Just make sure air flow is not interrupted so heat can dissipate from the motor

Sorry boss, this one I cannot say because I don't know what your plumber has done, or your layout.

You see.... everyone always say want high pressure water. But that is not accurate. They actually want high flow rate of water. Think of the difference when someone dumps a bucket on you vs wet you with water pistol. The first is high flow, and the second is high pressure. The bucket nice to bathe, but the water pistol is not.

Plumbing in M'sia always like CB. No system of proper pipe sizing, or pipe layout, or consideration for pipe feed. So all home owners end up putting a pump because to get a high flow rate can do by increasing pressure, but only to a certain extent. You just look all pump installed in M'sia - the pump is 1" outlet and then the plumber reduces to 1/2" immediately. How to pump properly? Have to put big pump at high pressure... then the joints leak. Should be 1" branch off become 3/4", branch off then only become 1/2" for proper water flow.

Sorry ah, long story. I know it is not what you are hoping to hear.