3 Simple questions from a newbie

1 - You have to go into the part and modify it's svg drawing and make it a custom part.
2 - You cut the trace by right-click deleting a section up to a bend point, size both parts in the Inspector, and then joining them back up again.
3 - The closeness of traces depends on how accurate it's going to be etched. Production houses can get them close, home etching depends on how good you are.