i think u have a mixture of issues here.
regards boot lock not unlocking with the central locking, id guess the motor has packed in on that lock, that would explain how it opens ok with the key
if your key doesnt turn the passenger door lock then id say the key mechanisum is damaged, presuming that key used to open it of course
when you say you have tried locating the switches, does that mean you have taken the door covers off and looked at the condition of them?
sorry you are having issues but on cars like these with electrical faults you just have to be calm and methodical, and really have a degree of electrical knowledge or they can have you over a barrel