The radio button's initial opacity needs to be set to 1, not 0. Otherwise the bullet is not shown on the initially selected entry, only after the first change.

The bug is also mentioned in the MSDN forum: https://social.msdn.microsoft.com/Forums/vstudio/en-US/c1aa5e04-bf61-4f37-9ca4-7cf1866c5ea8/the-bullet-in-a-radiobutton-becomes-invisible-after-applying-a-new-theme-at-runtime-via?forum=wpf&prof=required

This comes handy in various situations.

If the list box item is large and the text label short I noticed that the click-able area was limited to the text bounds. This should not be the case since the whole ListBoxItem area including the blank area should be responsive.

Example:
|xxxxxx                      |

In this case ShadeBrush seems more appropriate than NormalBrush, also to notice the difference between the hover behaviour.