Some Operating systems will allow you to adjust volumes for key clicks(so you know a key has been pressed.)
"my + is automatically getting typed while typing. " This indicates something is wrong with the keyboard. try shaking or blowing out the keyboard while holding it upside down. You can try lifting the + key out and cleaning around it with a cue tip and alcohol. Make sure It is not plugged in when doing this.
can you swap out the keyboard for another?