Ok my car smells like sulfer after battery died.

You need some punctuation in that huge sentence, otherwise it can be read three different ways. It sounds like there's two different but related problems. Rather than try to figure out what happened, it's easier to describe what typically happens. Since GM redesigned their generators for the '87 models, they have had a very big problem with them. Due to their design they develop huge voltage spikes that can destroy the internal voltage regulator, internal diodes, and can interfere with computer sensor signals causing hard-to-diagnose engine running problems. It is common to go through four to six replacement generators in the life of the vehicle. To reduce the number of repeat failures, replace the battery at the same time unless it is less than about two years old. As they age they lose their ability to dampen and absorb those spikes.

In your case most likely the voltage regulator shorted, system voltage went too high and overcharged the battery so severely that the case cracked. If there was a "Volts" gauge on the dash you would have seen it was much too high. The regulator is what runs the "Battery" warning light if that's all you have, but if it failed, that part might not work either. You would see that as the light did not light up as a bulb test when you turned on the ignition switch but before the engine started.

The battery has obviously been destroyed but I can't explain the 6 volts from the generator. What is important though is to not start the engine from just jumper cables, then remove them. Running any engine without the battery will result in system voltage going too high even when the voltage regulator is working properly. The battery is the key component in holding the voltage down to a safe level. Without the battery the high voltage can destroy everything that is turned on from the interior light bulbs to the dozens of computers.

Wash the acid from around the battery, replace the battery, then measure the battery voltage with the engine running. It must be between 13.75 and 14.75 volts. If it is high, replace the generator. Parts are available to repair them but GM made that extremely difficult. There's no way to test the internal parts and some of them can't be easily removed without damaging them. To replace all the parts that could have failed will often cost more than the cost of a rebuilt unit with a warranty.