[Bob Bengal]

Welcome to the forum, I'm not an expert, we'll see what the more experienced people say.

What I'd try, the fence doesn't have to be perfectly parallel to the front of the table, when you want to make a tiny adjustment you can loosen the knob just on one side and move that end.

How far is the bit from the fence and what do you have to measure the distance accurately?

 

[Bob Bengal]

In Euclidean geometry 2 lines, or 2 planes, or a line and a plane can be parallel. A point and a line can't be parallel. I don't know how to explain that clearly, um, a point has a location but it doesn't have an orientation. To be parallel both of the things need to have an orientation.

For a point and a line there is one and only one line (segment) that joins the 2 and is perpendicular to the line, that is the shortest distance between the 2.

Say you have a rectangular work piece and want to route 2 dados, 1" and 3" from the same side of the piece. Set up your fence 1" from the bit and parallel to the front of the router table, cut the dado. Now set the fence 3" from the bit but at some random angle to the table, cut the dado. The dados will be parallel to each other and at the spacing you wanted.