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04-01-2017 #1
You're probably mixing up the supply current with the motor phase current - the two are related, but the supply current will always be less.
You can avoid cutting the ground plane with one of the tracks by routing it another way ... not that it really matters for what you're doing.
It's a thermal limit and a cable is somewhat different to a PCB - try this:
http://www.4pcb.com/trace-width-calculator.html
3.3kOhms. But that's not the right question. You size it based on the energy stored in the capacitors, time in which you want the capacitors to discharge, and acceptable power through the resistor.
Crudely, the capacitors are discharged in t=5*R*C and the resistor power dissipation is P=V^2/R. I used a 3W resistor, but to get good lifetime from the resistor and not set fire to things it's a good idea to use less than the rating, say 2W. R=V^2/P=80^2/2=3.2kOhm. t=5*3200*0.02 = about 5 minutes.
Generally Onecall (farnell,CPC) or Rapid Electronics. Also Mouser and Digikey have started doing free postage on smallish orders, so they're good bets.
Be extremely wary of components from eBay in China - rife with fakes, especially capacitors. I treated myself to an LCR meter so I can at least check the capacitors.
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