Locked anti theft symptoms on a 2008 lincoln mkz.

What is your question?

I've had this car for a month so its still new to me. I only have 1 key the dealer gave me and its in a fob...not sure if its the main key but its my only key and it looks a lil worn. Randomly wouldn't start but if you tried it a couple more times it would start...I bought a new battery and didn't have any issues for a couple weeks and started doing same thing again and was happening more often...the anti theft light flashes and put the key in and turn to start there's nothing...no clicking or nothing. Sometimes when I put key in ignition it clicks as I'm putting key in ignition. You don't hear the fuel pump click in . Put jumper cables on it and it cranked over like it was gonna start but didn't. It could be the starter but since it tried to start we are ruling that out. Battery has been checked and its 12.5 volts, but when we was checking battery it sparked on the negative side so is that suppose to do that? Thinking maybe a short s omewhere or i accidently triggered the anti theft system

What makes this problem better or worse?

Idk I've only had the car a month now

How long has your 2008 Lincoln MKZ had this problem?

About a month