You are most welcome.
Where I refer to the "polygon of interest" in those paragraphs, I meant the polygon you are talking about from the IDF data where you said
The input I have from the IDF is a collection of points that represent a polygon that I'm looking for in the layout.
My point is that you cannot make any assumptions in advance about what that polygon might look like. It may be a completely odd shape that is nothing like a contiguous rectangle. In such cases, there may be areas that are included in the rectangle represented by the max and min X and Y values, which are not actually enclosed by the polygon. Kind of like a U-shaped motel with a parking lot in the center area - you can be in the parking lot (inside the extrema) but not actually inside the motel. So you have to figure out how to handle that kind of situation. If the route obstruct crosses the extrema but is not inside the polygon, do you want to include it in the results or not? Maybe you do, maybe you don't. I have no idea of the specifics of what you are trying to accomplish, so you'll have to analyze the objects you are working with, and the goals you have, and decide how to handle the non-simple cases.
The general method I outlined will give good results for all cases, regardless of shape.