About R1/R2 in the crossover circuit. I usually mount the crossover to the inside of the speaker cabinet, occasionally within a stand-alone crossover box. You can see the power curve on page 71 of the π Crossover document. The resistor doesn't get very hot at all. I don't know a specific temperature rise but I can assure you that it won't overheat and fail when covered by insulation.

They're designed for abuse such as this. Run 'em hard.

I'm confident they will work well for you and your church, day in and day out, for decades.