Thanks! I would say as long as there isn't anything missing in your application, don't worry about filling up all of your time. Enjoy your year "off", its often the personal growth that happens here that is important rather than the "academic-ish" growth. You already did that part, and if you did it well, now you can focus on other things.
It did come up in interviews, but not in any blatant way such as "so, I see all you did this year was a job, what's up with that?" It's more like, "so, what do you like to do with your spare time?" or "I notice you didn't continue with x EC after college even though you seemed to like doing it, why is that?" As long as you have answers to questions like this you will be fine. They will see you weren't sitting on your butt all day, and understand that when you get to the real world, you have too many responsibilities to have time for crazy amounts of ECs.
For me, if they asked any of those types of questions, I would just explain that I put a lot of time and effort into my job, and that one of my goals in my two gap years was to spend a lot of time with my family before leaving again. I would also mention a couple of hobbies that I spend time doing, such as working out and reading that aren't necessarily ECs, but do count as something you commit to and are dedicated to. All of my interviewers seemed pleased with this response. And, it was even stranger for me to have to answer this question because I lost my job (because of the sequester) in June, so I hadn't been doing anything from June through to some of my interviews. Even saying that I was taking time to apply to medical school to the best of my ability, and currently looking for new employment seemed satisfactory.
I really wouldn't worry about it too much, especially if you can say you were studying for the MCAT too, as that is quite difficult to do with a full time job. Also, keep in mind that for schools that do MMI style interviews, they will not even have the chance to ask you about it. I hope this has been at least somewhat helpful. Stop stressing and focus on crushing the MCAT! You'll be fine!