The alignment in this block has been fixed in the next release. This is a related to the font-size of the icon not matching the font-size of the explanation, and the way CSS tries to resolve the conflict is not always desirable. A fix is not to change the font-size of either, but rather to force a more desirable resolution to the conflict.
As for the line style, we long ago opted not to use the XenForo separator within the body of sidebar blocks, since the same separator is used by XenForo to both start and end a sidebar block. Adding it in the middle of one can look confusing or out of place, at least under the Default Style, and especially when the block is small.
Instead, please use Style Properties > Wiki Sidebar > Widgets, and adjust the border property to your liking. As the description indicates, this border is used as a separator inside individual sidebar blocks.