Thanks for recounting your experiences with your 164, I don't think we have anything so spectacular - may be all to come?
Can't help with the interior lights problem. I take it that they are utterly dead, by that I mean it's not just the 'coming on when you open a door' bit which isn't working?
The boot release problem - have you checked the relay or solenoid?
If your car is the same as our '93 model, then the relay is located inside the boot on the RHS - pull back the boot trim near to the fuel filler pipe and you'll see it, together with another (similar) relay which operates the fuel filler cap solenoid.
The solenoid for the boot release is wired from the N/O contacts side of the relay (the heavier wires) and is in the boot lid next to the lock.
I can't remember for sure, but I think that the two relays share a common 12V wire for the two coils, which loops from one to the other (red on ours). I think the switch on the dashboard, when pressed, closes a contact in the coil return wire to energise the relay.
When you hold down the button on the dash you should get a continuous 12V signal to the coil (i.e. it's not a pulse signal) so if you put a meter on it and get someone to press the button you should be able to see the coil volts sit at 12V if all is OK from the button!
This should also allow you to prove whether it is the relay or the button on the dash which is defective. If you get 12V in the boot, then thank your luck stars it is not that switch panel or vehicle wiring somewhere - you should be able to trace it down to the relay or solenoid, with any luck.
Hope that makes some sense and helps!