Advice for High Side Switch (High Current, Low Voltage)
"If it's rated 30V/1A (30W), could we assume that it would be okay at ~6A at 5V?" - No, as the current would obviously exceed the maximum rating.

You can use the below circuit to switch your load:


You'll have to look for a PMOS with appropriate current rating and a gate-source threshold-voltage below 2.5V, though.