"then i drove for about 20 min and the pedal started to stick a little and the car started sounding like a toy wind up (whinning)"

If the pedal is sticking, it can very well be improper bleeding of system, bad slave/master cylinders. As for the whinning, sometimes if the throwout bearing isn't properly pressed onto the cone (cockeyed), it can produced a whinning noise. Now, I have owned MANY 240sx and the throwout bearing whin seems to be pretty common amoung the model.