I wish there was a way to have different coloured onion skin outlines or a way to colour the points something different especially as this character was a teal green.
Just view in wireframe or set the prefs colors for the vectors to a different color. You can switch back easily later.
About bone locking... when you lock a bone and rotate parent bones of the locked bone it is going to naturally cause a nightmare if you unlock that key. I've had pretty good luck fixing "wobbly" knees. Rather than rotate bones to fix pops and such, use the SCALE bone tool... just slight scaling along with rotation will ease the bone into position.
Keep in mind what AS is doing... it is using the chain of bones to create "IK Targets" from the locked bone. So when you try to force a position it can't reach with the bone chain... it gets stuck and causes those pops and wobbles.
It can't reach the exact position you want because it isn't physically possible to do it. The length of the bones, maintaining the locked postion.. it just can't reach.
That is why slight scaling of one of the parent bones can help. It isn't noticeeable if it is slight and also "covered" by a rotation. This is tricky even in some 3D software. Animation Master gets those weird popping bones in some of the rigs.
-vern