The audio driver has nothing to do with the speed of the games in DOSBox. The fact that you are running at only 4000 cycles is why. Try around 10,000 cycles.Often the Sierra Games are quite slow under DOS-BOX, because Sierra had shitty Audiodriver. I used a Patch Programm called GOSIERRAV3 to Patch the Audiodriver.
The speed bug with the Sierra SoundBlaster was only with initialization of the driver. As you have found, the GOSiERRA patch does not always work and may take multiple launches to work.
DOSBox allows you to use the old Sierra work around for the SoundBlaster bug, which was to turn off the turbo switch to start the game and turn it back on after the game has started. Start the game in DOSBox with very low cycles and then increase to ~10,000.