that 10 way connector is all about the seat heating, under the passenger seat there is a black box, this black box controls the heating on both seats so, the 4 big cables are power in + - and power back out to the diver seat + - hence the driver seat only has 2 big cables. the other small cables 2 passenger 1 driver all report back to the heater controls under the stereo
i'm guessing you don't have seat heating in your old seats so basically tuck it up out the way and don't worry about it
so 2 other things 1 i've covered already making up the resistor plugs and getting someone with vcds will remove the airbag light
2 have you ever had the seat belt chime turned off on the instrument cluster, if so this is why your not getting the bong when you drive regardless of having the seat belts clipped in?
both the driver and passenger seats report back to the airbag module for seat belt/occupancy , i'm pretty sure though regardless of this working both airbags will still go off as its only the same as not wearing your belts like some people do, if they have a crash the airbags always still go off, so up to you really if you even want to install the seat belt/occupancy system