a) how long are sequence power cords? would they run fine using an out door extension cord?
6-7 feet.. I too lazy to measure mine but that is rough estimate
b) are they weather proof?
Yes they are weather proof but not waterproof. Meaning that this pump cannot be submerged in water. Althought I have seen some pumps that were under water at pskoi they were still working after all that..
c) if i need to make a housing for the pump, do i need to keep the pump 100% dry? would some moisture destroy the pump?
It doest hurt to keep it dry but this pump can with stand some rain..
d) how effective are the leaf traps/priming pots?
Use them cause if you dont the pump will clog up with algae leaves etc which in return will make your pump work harder and draw more power.
e) if i restrict the flow going OUT of the pump, would it do any long term harm?
Restricting the pump will not harm it but will make the motor work harder and draw more power. Its best to let the pump run free.. Hope this helps sorry I was too lazy to measure cord.. 