Ford Taurus. No One Can Figure It Out. PLEASE HELP

My 2006 Ford Taurus shut off while driving.  I replaced the alternator but still
will not start. Everything works when the key is in ignition except for the
speakers but the radio turns on.  When my friend tried to use his code reader
on it, it said it couldn't connect.  I have check all grounding and fuses. I have
replaced alternator, neutral safety, ignition switch.  I was told problem is
electrical somewhere from the ignition switch to the neutral safety.  The car
will try to start if you hit the contact on the starter relay but otherwise there is
no crank when turning the key.  I am very tight on cash and have run out of
options. I have literally tried everything. Please tell me what it could be
because I am about to give up.