Can't help with some of your probs but:
LEDs with LCM is more trouble than it is worth IMO.
To fix the soda spill problem you have to remove and clean every thing out of the car. Soak in hot water and then dry. Check car wires for damage - I guess the sugar etc will have attacked the plugs and sockets and maybe the wires. Hot water soak using a cup or mug may work. Hair drier to dry the plugs and sockets, WD40 spray on assembly. Don't forget to inspect the earths.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 White and 1 Light Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i