1. If you're getting the message but a colleague isn't, this most likely means that the listed fonts aren't present on your computer. To fix this, run a search on your colleague's hard drive to find where the fonts are stored (It's a common Windows folder). Just copy the whole folder, and take it to your computer. Find where your computer keeps fonts (should be similar or same location) and swap the new fonts folder in. Of course, back up your fonts folder first, just in case there's something unique in there. Fonts can be added individually if you prefer.)
2. The screen shot of your ctb shows that you're using the default monochrome.ctb. Notice that it says 'lineweight: Use Object Lineweight' ...this means that whatever lineweight is assigned to the object itself is the one that gets plotted. Have you always used this ctb file? Most companies make their own to use. Anyway, if this is how you have to do it, then start looking at layer and object properties to give the text a thicker lineweight. I wouldn't edit the ctb file to get what you want, unless you plan to share it with other users. Remember, they have a file with that exact same name on their computer, too. If you change yours, theirs will still be the same. (Unless you have your ctb files on the network.)
3. Does your colleague have problems when plotting? If not, adding the proper fonts to your computer may do the trick.
4. FYI: Font substitution, as a thing, should only exist when plotting to pdf. This should mainly be used if you are using an AutoCAD-specific font (shx fonts). Reason being, as I mentioned before, everyone else uses ttf fonts and a lot of software can't really work with the old shx fonts. So, font substitution is the way around that: essentially, you're mapping an shx font to a particular ttf font, so that the pdf writer can properly generate the text. Unless you're only seeing this issue when plotting to pdf, it's very unlikely that font substitution is having an effect here. (To clarify, 'font substitution' as it relates to making PDFs, and the substitution message you get when opening a drawing, are two completely different and unrelated things. They just use the same words.)
Jim

Jim Seefeldt
Electrical Engineering Technician