Wow....I mean...wow...my friend, you must be an AVID gambler. Or you are really lucky!
Assuming that this content is on tribble, then he could have just earned 500,000 GPL through the prototype consoles or through the regular means and just copied his character over a few times. I would have preferred some treasure besides latinum bars like Flame Gems.
I imagined killing 1000 Breen npcs quite impossible, given that the only opportunity we have to fight them is in 4 episodes that can't be repeated.
Transphasic mines currently count as Breen ground troops so you can get 20 a day from the Satellite Repair mission. Also you can get 10 transphasic mines from a Kelvani belt mission where you are surrounded by mines. It is the one with the destroyed mining station not the functional mining station. Most people that have that trophy, farmed for it. I played the last mission and didn't talk to the science crew, then I dropped the mission. Repeat the mission until you get the trophy. If you have done everything, then your only choice is the Satellite repair mission.