Currently there's no saved game editor of which I'm aware. And those continent bonuses are generated at startup, so I imagine you're stuck. There might be a dev console command to change them, but I very much doubt it.
Regarding the third weapon upgrade option, you may either:
It's worth mentioning, as someone who's completed two campaigns and is halfway through two more (only one of which had Armed to the Teeth) that it's completely unnecessary and fairly overpowered below Legend difficulty. That said, if you want to have it, go get it. I personally think it's not well balanced with other continent bonuses, so I won't judge.