OK.
Well there were a number of issues. The main one that related to dimensions were that you set softening way too high and so the Dimension tool had a difficult time picking end points to snap to. You could turn on Hidden Geometry (View menu) to see the endpoints you need to snap to. Better is to correct the softening so that the sharp corners are visible. Another problem, related to attaching dimensions is that your style has Profiles turned off. Combined with the over softening, that makes edges virtually unselectable. There was also a bunch of extraneous geometry that got in the way.
Here are the things I did to your model to make it easier to work with.
Changed Units to Fractional. Since you are drawing a house, you don't need architectural units.
Adjusted the style so Profiles are on but set to 1 so the profiles aren't displayed as thicker lines.
Unsoftened all the geometry.
Cleaned up extra edges and coplanar edges that weren't needed and removed an unneeded internal face inside the front fender.
Corrected face orientation. Blue faces are supposed to be on the inside. It's a good idea to maintain good housekeeping as you go.
Softened the edges again but only to about 20°.
I also did some other things such as replacing the left side fenders and running board component with a flipped copy of the right hand one. There's no need for them to be different components. I moved the geometry inside the components to Layer 0. Only components get layer associations other than Layer 0. Also, make sure you always leave Layer 0 as the active layer. Create all new entities on layer 0 and make other layer associations as needed. Finally, I purged unused components from the In Model library to reduce the file size. In this case it reduced the file size by over 80%.