Ok, I have an e36 so I will help even though you are asking the wrong crowd here. You may be using the valet key which wont unlock the trunk or your trunk lock is busted, try using your other key. If you still can't unlock it you can us a coat hanger to release the fold down seat then pop the release inside the trunk. If you don't have fold down seats, there is a trick that involves a drill and some luck.
There is no security code for engine start on the e36, just a code to use the radio itself. I would say you have some wire rot or a bad charging system. If it has an aftermarket security system you will have some issues with power loss as well.
Spraying gas into the intake of a BMW is like pissing in the wind, you can do it but results may be bad. If the pump and injectors aren't working, no amount of intake spray will help. If you had an M with individual throttlebodies, it would damage them.
Go over to the e36 forums or look in the M forums for pre OBD I guys that may get you some help.