"So for this missed approach "when established on track 300" effectively/practiaclly means once you've rolled out on your drift heading?"
Yes, turn left to make good a track of 300 degrees.
"Why do the MAPts appear to vary by 0.1NM between the plan and profile diagrams?"
Can't see it! On my chart (Jepp) the MAP is 11.6 nm from the SY DME on both the plan and the profile.
"when a procedure turn is required during the approach .... it is not intended to intercept that track from the aid, only to turn onto a drift heading (DR track) immediately after passing over the navigation aid or fix"
If my interpretation of your question is correct, Yes!
But I am not entirely sure I have the question right. Give us a "fur'instance" chart!
Dr 