Short answer, yes. The skills you learn through FCC, and through the research you also include (there are some lessons that will force you to look outside FCC, notably MDN or http://devdocs.io/) will stand you in good stead in terms of getting a job.
Absolutely, build your own projects. Get involved with other open-source projects, as you feel you are able. Get involved with the community of developers, and both ask and answer questions.
Many developers experience “impostor syndrome”, where we may have great skills and abilities, and even experience, but we feel like we’re faking. We question ourselves, we question our abilities, and we don’t allow ourselves to pursue opportunities that are there for the taking.
That, more than skills or certifications, is a challenge to overcome. You are good enough, and you are getting better with each line of code. Good or bad code, you are improving. You are learning what works, and what doesn’t.
So yes. The FCC cert will give you, on an objective level, the skills you require to perform as a developer. On a subjective level, there are things like the marketing, or the personal worth, or other issues. Those are of a far larger scope.
Best of luck!