Matt, it looks like you have finally found THE yellow wire make sure it is connected to the battery + and you should be away. That wiring looks a mess tho a lot of it is non standard and makes it more complicated than it should be, what is the relay for?? Tear it all out and make it simple as per stock escort wiring, then add extra wiring as required for your application.
You should connect both the big cable from boot and THE yellow to the starter , and piss everything else off. Put 250a fuse on battery and 60a on yellow wire to be perfectly safe. That is what i have on my escort.