Part 1 Preparation.

For example, I use the letters "JAC" from your file.
1 Let's remove everything unnecessary and zoom in, it's more convenient for me.
2 Let's block the oval, it will come in handy later.
__1__

1 Since we have to change the points on the curves, for more precise control of the shape, create a copy of the letters and lock them.
Select all font curves, copy, block and paste by pressing the appropriate command buttons.
2 Let's leave the letter "C" selected and turn on the control points on it with the "Show pts" command.
__2__

This curve has three disadvantages: a large number of points, their uneven distribution, and the presence of corner points.
__3 - 3_2___

First, let's prepare the necessary parts.
1 Separate the curve.
2 Deselect the straight lines.
3 Combine the remaining parts.
4 Let's fix it with the help of the 'Rebuild' tool.
__4__

1 At your choice, use "Refit" or "#Points" mode.
2 If necessary, correct the curve with the help of control points or by pressing the line with the cursor in the desired location. The blocked copy will serve as a reference.
3 Correct the inner part in the same way.
4 Hide the control points.
__5 - 5_2___

End of Part 1.
To be continued ...

This is a link to the examples files:
https://disk.yandex.ru/d/iZJs9cXoL0mqPA
https://disk.yandex.ru/d/vz00zq3ufVD2cg