I have to add 3 new conductors to a 75' long conduit run. 1/2" EMT conduit, all #12 conductors. All existing conductors are solid. The three new ones I am adding is stranded #12. I also want to delete an existing solid conductor (wrong color). There are six conductors in there now. I understand the max is 9 for #12 in a 1/2" conduit. So this would be very tight. Since I am taking one out, I will end up with 8 in there. Is it better to remove the extra wire first, then use fish tape to pull the three new conductors? Or is it better to use the existing extra conductor as a fish tape to pull the three new ones? If I use a fish tape, with the existing wires in that conduit, should I pull one at a time, or all three in one shot?

I had the builder install a box on the back of my house for my future building. Now that we have settled in I now have the building put up and dug the trench for the electrical. When I removed the cover on the preinstalled box I found two 12/2 sets of wires. I called the electrician and he checked to find out both wires lead to the one breaker in the main panel. He said I could get a tandem breaker but I thought it was their job to do it right. I have learned that it should gave been 10/1 or larger gauge installed but the wire cant be pulled and replaced. Can I have both wires somehow run to the building to get two 20amp feeds. Help!