Even if we assume that he is smarter than you or better at engineering, that isn’t all that matters and it’s not all that makes someone “deserve” a job. Even engineers need a modicum of people skills. They need to act professionally, they need to communicate effectively, they need to be able to take direction and manage other employees. The fact that you interview well isn’t meaningless; it’s probably related to a host of other skills that will make you a good employee, not just a good engineer. Your boyfriend should work on developing some of those skills himself, or he could end up being a great engineer and a lousy person to work with.