At the moment the CPU is varying between about 62-70% during playback, memory is 61%. All of the suggestions & tweaks seem to be paying off though, I'm hearing no distortion (unless I start moving the mouse around, which makes it distort immediately).
If the CPU is running 70%, consider it as being "maxed-out" for the purpose of anything requiring real-time processing. Clearly, there's not enough spare capacity to move the mouse
I really think that replacing that laptop with a more powerful unit is going to be the direction you will ultimately need to take. I feel you also agree.