The first thing I want to say is you would have some of the issues on your list even with a filter solution because they are all CSS issues.
The reason the post counts are a different color than the category names is because the category names are links and the post counts are not, and your them styles links differently than plain text.
adding this to the stylesheet should change it
.avhec-widget-count { color: #96A1A6; }
Note that the link changes color when hovered over. The count is not going to change color when hovered over.
The bottom border is assigned to the A link tag. Because we are floating the A tag to get the post count on the same line the length of the A tag is only the length of its contents. The border can’t be any wider than the container it is a border to.
The bottom border will need to be assigned to the LI tag that contains the AVH div and the A link within in. Then it will be tricky to get that bottom border to display only on the LI tags that contain AVH content. It can be done but it is tricky.
as far as bottom padding, to that block of CSS i gave you before add the line
padding-bottom: 3px;
then adjust 3 px until you are happy with the result.
for the arrow movement on hover:
.widget_extended-categories .avhec-widget-line a:hover {
background: url("images/shared/icon_arrow.png") no-repeat 2px 1px;
}
I am busy today and can’t put any more time into this until tonight at the earliest.