How does the Anti-Theft-System work

To give you the full information, I like to tell you a bit more about me and the car(s).
I'am from Germany. 5 years ago I bought a 1991 Pontiac Bonneville SE 3.8 just to have a car to drive the daily way to work and back home for a few month, but now I have it for more than 5 years. It doesn't takes long that I started loving this car.
A few month ago, I got the chance to buy another one, an 1990 Bonneville SSE 3.8. The cars are more or less the same, but the SSE has a few more interior options, like sun roof, leather seats, etc. And also an Anti-Theft-System.
The SSE was not in a good condition when I got it, because the previous owner placed it in a yard next to his house for around 10 years without driving it, not knowing that just the fuel pump was the issue that it won't turn over run. - For me this was a quick fix to find out :-)
Due to its downtime, the door locks were rusted and it was not possible to turn the key in the locks, so I ordered a full set door locks (doors and trunk) at RockAuto. The door locks I've ordered fits perfekt to the doors, but at the backside, where you put on the linkage, you also have to put on a switch for the Anti-Theft-System, which is not possible, because the admission of the new locks is too short.
Now the Anti-Theft-System-Light in the dashboard is on or flashing.
The Anti-Theft-System-Light is permanent on, when you CLOSE the power-locks with the door lock switch on the door panels inside the car.
The Anti-Theft-System-Light is flashing, when you OPEN the power-locks with the door lock switch on the door panels inside the car.
In any condition, it is possible to start the engine and to run the car. If the engine is runing, the Anti-Theft-System-Light is off.
The only issue: if you leave the car for more than 20 hours with the Anti-Theft-System-Light flashing or permanent on, this will kill your battery power. Just to take out the bulb from the dashboard won't fix the issue, because the Anti-Theft-System is still working and also takes the power from the battery.
The final question is: how to modify, or better, how to eliminate the Anti-Theft-System, because it is not necessary to have it working for me.
For me it is just important to open/close the doors/trunk by using the pysical key, to have the power-lock function working from the door panel switch and also to open/close it with the remote control.

Many thanks for your support.