From One (rare) UK Crossfire owner, to another...
1. Is the Reversing camera tapped into the rear lighting (reverse light)? You might have to remove some rear trim panels to locate the cameras wiring and isolate it (disable it - to see indeed if this is significantly contributing to the problem). Or if it's wired back to a Fuse box - pop out the fuse and see if this reduces the drain.
Plus how do you view its video feed? An aftermarket screen up front or some other method? Perhaps that is wired to a permanent live (could be another potential power drain).
2. Concerning the cigarette lighter. Does the glove box light work? If not, change fuse number 31 in the engine bay fuse panel. If you've checked other fuses, might be a dead socket! That you would pull out and replace. If you get to it's wiring, you can at least put an electrical tester on its contacts to confirm it's got power.
Also, could there be physical damage to the socket or the lighter you plug in, hence its not mating properly and operating? If a child has been playing around with it.
3. Faulty Power Seats Relay (main culprit). The relay is located behind the firewall. Plus the operation of the electric seats does matter if the doors are open or closed (apparently)! Mine is the same actually, the controls on the side of the seat sometimes work, other times nothing!
4. Perhaps try re-seating the Connectors in the back of the stereo? Quick spray with a contact cleaner might be a good idea too. If issues persist, might be time to relace that Infinity (or upgrade)!
With the internet, there are so many car websites that provide guides on troubleshooting electrical issues / "parasitic battery drain". Also there is youtube as well. Plus the advice can be applied to all motor vehicles generally. You shouldn't need to pay someone to resolve these issues, if you are methodical and follow the guidance here, plus that you find online...
As stated above, if there's an issue with the Crossfire, it's most certainly been brought up on this Forum in the past. Search for it and you'll find how others have resolved faults.
Best of luck!