First time building a bike from the frame up. I am confused on how I should route the shift and brake cables.

This is the Seaboard/Tsunami CX03 gravel bike frame. It is made of chromoly steel.

There are 2 internal cable slots on the downtube, and one external cable hanger.

I am using the Shimano 105 R7000 groupset and mechanical disc brakes. Until GRX comes out with crankarms that are 160mm or smaller, I will have to use the 105 crankarm. This is why I am sticking to having a front derailleur. When most people build on this or similar frames, they use a 1x drivetrain, so I am unsure where to put the front derailleur cable.

My cables are the Jagwire 2X Sport Shift Gear Cable Kit and the Jagwire Pro Road Brake Cable Kit. I just tried opening the Pro Road Brake kit, and there is only one cable. I am questioning whether I will have enough for both front and rear brakes.

How should I go about this? I would like Left brifter to be rear brake and Right brifter to be front brake (I apologize if this is not the standard layout!). So I was thinking to have the Right brake cable cross in front the headset and down the fork to the disc brake.

In the picture above, I labeled 5 positions. After that, do I put the Right shift (rear derailleur) cable in #1 or in #2? Do I put the Left shift (front derailleur) cable in the other slot, and hang the rear brake cable on #3, or the other way around? If I do hang the rear brake cable on #3, do I wrap it under the BB (and induce rubbing) or hang it over the top of the BB to reach the brake?

All advice on how to route the cables would be highly appreciated! Thank you!!