Ok, you're going to need to jump through a few hoops to get this to work.

You'll first need to cut the 2 curves up at the 4 hard corners of each curve.


(Note: this was for display, don't move the curves apart like this.)

As previously mentioned, one of your curve's seem is in the middle of the large arch of the "C." When you cut your curves like this, the seem will cause the outer curve to be divided in half. Attach it together to form the one curve using the "connect" option rather than blend so as not to change the shape.

Next, rebuild each individual curves so that they match. For example, the large round outer curve when I did it was 10 spans. Rebuild its counterpart curve to be 10 spans and with the following settings:


(Note that the number "10" in this case is an example. Your numbers may vary.)

You can determine how many spans your curves have by looking in the Attribute Editor while one is selected. When comparing, you always want to rebuild BOTH curves to match the higher number of the 2. (Even rebuild the one who's numbers you're matching to get rid of inefficiency caused by the curve detachment.)

The small curves making up the ends of the C were both 1 span, but still rebuild them to be 1 span with the above options so as to clean the mathmatics behind the curves to result in clean geometry.

Etc.

Once your curves all match each other and are rebuilt, you can loft between the different sections. Once you have all your lofts, you can attach them together using the "connect" option rather than Blend to keep the sharp corners.



Enjoy.