Spot Colors saved in my Library being converted to CMYK

You may want to vote here:

https://illustrator.uservoice.com/forums/601447-illustrator-desktop-bugs/suggestions/34291627-pantone-solid-spot-colors-added-from-indesign-to-a

Yes, that is a known problem. The best and safest thing to do is to create objects filled with the spot colors and add those to a CC library.

Spot colors are not very well supported in CC libraries.

But as a workaround you can drag an object using a spot color to a CC Library

You can also drag multiple items using different spot colors together into a CC library to simulate a library.

The easiest way to add them to a new document is to hold down the Alt key when you drag them from the library and place them in a new document. The spot colors automatically added to your swatches panel.

You can hit escape before you click to place the object(s) or delete the dragged library items because the swatches are now part of the document.