how can i change line width of cutting line and detail circle only?

I took a look at this and it seems questionable. The "section line" is a Geometry line weight and the circle is appearantly leader line weight. This is pretty much locked in as I cannot seem to select the circle as a "curve" nor access section line geometry. I haven't seen anything that assigns line colors specifically to section elements. If this was the case, then you could play with the pen tables.

My tests are done with standard ASME settings. I don't know if other standards would yield different results. I suspect you are simply expected to follow a known convention in this regard. Kind of silly not to open this up to user preference.

One thing I did note is that you can "Break" the section line if that helps clarify a view.