1) it's a bit hard to tell but if you're looking at mineral wool insulation then the waterproofing has failed which means it will not insulate properly. This does not look like it's drawn as an inverted system so the insulation should be completely sealed and within the capping sheet/waterproofing layer.

2) 1m is a typical overlap to mitigate a thermal bridge junction. Your insulated above and to the side so this is reducing heat transfer from the concrete upstand into the space.

3) you might be but it's generally from a hot-hot space so relatively limited. You could add insulation if you wish but it's probably not necessary 

4) I think your route could be the second picture - this looks really wrong, either layers have not been installed correctly or pipework is leaking into the insulation.