1998 3.8 Camaro Will Crank But Won't Turn Over

So I bought this 98 camaro with a 3.8 in it that
needed the manifold gaskets replaced. I did the
repair, put everything back together right,  and now
it won't start when I try to turn it over. It'll begin to
start, until I let the key go then it dies. I can hold it
in start and press the accelerator to rev the engine,
but once I quit doing that it still dies. I have every
sensor hooked up. Two possible things. It could be
the anti theft system, cuz when I got it back to my
place and tried to back it into a parking spot it died
as soon as I hit the accelerator to reverse and the
transmission locked.
Or, when I toom the alternator off, the wire going
into the clip broke and a buddy of mine who used
to make wiring harnesses fixed it by taking the clip
apart taking this metal thing the end of the wire
went into and put it in the same hole where the clip
plugged into. Could be that but I don't know.
If there's anyone who could shed some light on this
ordeal, you'd be doing me a service and I
appreciate it.