1) UCCNC is $60, plus $125-$150 for a USB or ethernet motion card from CNC Drive.
LinuxCNC is free, but if you don't have a parallel port, you'll need to spend about ~$100 for a Mesa ethernet board.
There are low cost Arduino based controllers running GRBL.
2) Fusion 360 is free, and very popular. There are lots of other options, depending on what you want to do. Look at F-Engrave for free V Carving.
3) A breakout board is typically the interface between your stepper drives and your PC or motion controller. It's the controller that will have a USB interface, not the breakout board. Although some controllers are both controller and breakout board in one package. Most controllers only work with specific software. See #1 above.
Breakout boards can be as cheap as $5, and as expensive as $200, depending on features, and whether they are made in China or not.