UPDATE
for my first problem of not seeing the reconstructed volume in real-time during the US acquisition, I noticed that having the reference I used for the spatial calibration, visible by the tracker solved the problem. I think I wrongly configure the xml configuration file and made the reference presence necessary for the volume reconstruction. Is there an example of configuration file for live reconstruction that does imply using the US probe only (without reference) ?
And if it can be of help for anyone, I solved the US image quality problem by setting the US parameters in the visualization software Echo Wave II, while Slicer is running. And with the help of this post I tuned the contrast and brightness in Slicer viewer using the window/level mouse mode