I regarding to your question how to handle 3D gauge:
I want to remember that you have the text property which could be used for showing a values but also a general text. Please , check the text attributes property of this widget where you can change the appearance of the text. By default the text Attribute property of the 3d Gauge widget is set to “fill:rgba(255, 255, 255, 1);textbaseline:middle;textalign:center” but this could be change.
If this is not enough for your requirments you can also use of course a 3d labels but I could not understand what should be there an issue when you set the possition. Ok if you have an dynamic position of the 3d gauge you have to notice the shift between the corrdnate and then e.g. by $watch construct where you can update the coordinate of the label in regards of the gauge coordinates ... some think like: