TOC space issue between header and dots

Not being able to see your screenshot example, here are a couple of things I'd suggest that may fix your problem:

1. Go to the Type>Show Hidden Characters menu command to turn on light blue, non-printing indicators for every space, tab and indent, among other things. It's the same as Microsoft Word's "Show Invisibles" command. The most prevalent reason for uneven spacing between text and tab characters are unexpected spaces and tabs between the text and the start of the dot leaders.
2. If you've used one period/dot character for your dot leaders, try putting two in there. InDesign lets you place up to two characters in that Leader: edit box when you set tabs with the Tabs panel or your Paragraph Style Options dialog boxes. This also has sometimes helped InDesign users who have uneven spacing between text and tab leaders.

Please let us know if one of these options help you. Or, if they don't. Either way, folks here are happy to help you get through your tabbing issues with InDesign.

Randy

 

instead of these dots I recommend to use a dottet stroke. Create a character style with underline. The underline uses a dotted stroke (you can either create or define one for yourself). The character style can be applied via nested styles automatically. 
These strokes show better regularity and are more flexible. 

Your page is not loading (many attachments are getting stuck at "virus scan" these days!) but what you want to look at is the ability to apply a character style to both the TOC page number and the space in between the item and number. The latter should let you define a font size, spread etc. that optimizes how leader dots or other characters fill the space.

Some variation in the end spacing is unavoidable, though. You might try using <space><dot> or even <space><dot><space> as the leader definition; that sometimes gives the tab enough springiness to minimize the gaps.

Looks like you'll need to upload your screenshot again.