Oh my that's quite the gap. How straight is the toe plate with the rest of the toe line?
I think I know how it happened. You used a file cross-wise in taking the surface down rather than lengthwise. You need to use a tool that engages the whole surface area at once when you're getting down close to the end depth. Be careful with the free end that you don't take more off there too and wind up with a bend in it.
I see another problem too. It looks like the tip of the toe is somewhat rounded off and not sharp. Again that probably happened from using your file cross-wise. I suggest leveling the whole totality of the toe plate area and then glueing a patch of wood that engages the whole area, and will fill that little hole that is going to exist at the pointy end of the toe plate. You're probably going to have to make another one too, because, from the pictures, it looks like it's going to be a little short.
In clamping down your wood patch, the BEST way to get it really clamped down tight is to use pan head screws with washers and little shims under the sides Or use your toe plate (with washers over it to keep it from bending upwards, and the shims. It'll be almost impossible to get clamps to engage without wanting to slip. The screws are going to come out anyway, and the holes covered so it's not a big deal to drill these new holes
Toe plates shouldn't be filed to their final lengths until they are fully fitted and installed--screwed down tight. You should also cut your inlets a little shallow so that when they are screwed down, they are a little proud to the wood. It's easy to file them down some as well as the screws. Just make sure you cut the screw slots a little deeper BEFORE you start filing them away!
Another reason for that is that it's about impossible to not cant the toe plate slightly from one side to the other if you're not using a jig. Filing it afterwards will take those couple of thousandths off the high side.
The wood is going to swell and get proud to the plate during the whiskering process too, so your engraving in the TP might need a little freshening up as well. The wood is going to move somewhat seasonally anyway, so it will NEVER be PERFECTLY smooth in the transition between the metal and wood. All you can ever do is get it really CLOSE to smooth for at least PART of the year.