You should power the FC with the BEC built into your ESCs, not directly from the flight battery. That is a 5v or 6v regulated power source.
FC power wires are all connected directly together so that power from the ESC/BEC goes in the FC ESC ("servo plug") connection and is available at the FC's receiver port, mainport, and flexiport, and one of those is connected to the receiver.
The FC is designed to be able to be powered from more than 6v, but it is not recommended because it causes a lot of heat and can lead to failure. I don't know the max voltage of your receiver. You could look that up on the internet.
Regardless, of the issue, the receiver is very probably damaged and you will need to buy another one. Any time there is smoke, assume that something just got destroyed.