Please add wireframe view for this document.

You didn't convert object to CMYK, you see Pantone values as object is in spot color.

It is absolutely not a problem, since there is only 3 shades of 302C used in the document. You can easy transform them back to corresponding Pantone. Just take same Fixup and modify it to convert to spot by searching for a correspinding CMYK value. Background is already white so it will not affect the result.

This plug in does work in PS CC

One ico file will always be only in one resolution. For every resolution you need to save separate ico file. Just record action for all resolutions and run it on every PNG file you need to save. If you are not familiar with Photoshop Actions, take a look at this brief explanation: helpx.adobe.com/photoshop/using/creating-actions.html

Main reason why I made conversion to CMYK is because in headings 302C is 100%, but in background is only 10%. So by converting to CMYK I can target only background color and don't touch headings.

I don't think that for this small purpose Pitstop Pro licence would be a good investment.

Draw rectangle, erase part that shouldn't be visible with soft brush.

Printing to PDF printer will save you a lot of abracadabra you are doing as for Illustrator PDF is native format like AI that you will be easy modify after.

The only thing to keep in mind and what is not mentioned in Wikipedia — adding edge index to your design will easily expose any binding errors. I.e. If folding of printed sheet will be inaccurate, the index pages will start to jump and will not form accurate one to the other. Your sample image also contains this error.