Since my monitor is limited to sRGB, is CMYK color space fully visible within sRGB, or Adobe RGB color spaces, or not? Conversely does CMYK have a converted NTSC color gamut % like sRGB or Adobe RGB?
The simply answer is: No
The complex answer is: Not fully.
Every picture of colors gamuts will show and tell you that although CMYK is contained within RGB there are few colors that go beyond the RGB.
Remember that color profiles have also influence on how colors are showed on monitors and how they are calculated to CMYK. And yes, CMYK have a converted NTSC color gamut but still will not produce correct results. Especially in the "green zone"
Strictly speaking, no. There are colors in the CMYK color space that are not visible in sRGB or even Adobe RGB. But you're less likely to encounter them.
Reds, Greens, and Blues are way more commonly seen in imagery than Cyans, Magentas, and Yellows. So unless you have a lot of imagery of daffodils and Caribbean seas, you'll need to worry more about colors that you can see in RGB but not CYMK. Luckily Photoshop has a gamut warning (under the view menu) to show you this.
You still need printed proofs. Even if all the colors match, things look very different in print than on a monitor.