The ECM (computer) develops parameters over time during its operating life. One of the most important inputs it requires and uses daily is throttle position. This input controls fuel delivery under load, wide open throttle, idle, transmission kickdown (automatic) and cruise. The problem with throttle position switches is that they are a potentiometer with a moving component to send a signal to the ECU. Over many years this friction wears out the potentiometer, however the ECU retains the parameter information and doesn't much care over time for this wear. However, when you disconnect the battery, this memory is lost and the ECU then has no idea of the throttle position due to the mechanical wear of the TPS. End result being a computer with no idea how to deliver fuel over an operating range. The best solution is to buy or borrow a new TPS from a reliable source, and drive the car for about twenty minutes under various conditions. This causes the ECM to "relearn" and if you keep 12v power constant when you replace the donor TPS with the old TPS, you can return the new TPS to whomever you received it from, and the computer will be back to its old self. The end result is your car is running fine (for its age!) and you wont have any starting issues with your new battery!
For clarification, the acronyms "ECU and "ECM" are the same item, I use these abbreviations in everyday speak, ECU stands for "electronic control unit" and ECM stands for "electronic control module' they both refer to the same component.