Trellis got introduced in 6.6. Since, you are on 6.5 you can remove the lines with validation error (Do check out trellis example it is a cool new visualization feature).
For reducing the size of Single Value font, you have two options:
Option 1) Simple quick fix is to reduce the Single Value Panel height which reduces Font Accordingly. Following is Simple XML code for the same
<option name="height">100</option>
Option 2) Through CSS you can override font-size of specific/all single value results using !important in CSS (add to existing Style section).
.single-value .single-result{
font-size:75% !important;
}
PS: You will have to make changes as per your need. I have give percent option so that you can easily change and understand impact.
Absolute numbers are displayed in HTML Panel with their respective CSS Styles you can override as per you need.
Finally color ranges (grey) as you have intended can also be done via UI. I think currently since it is on Percent Trending it should be Grey for 0%.
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