I have just finished a lengthy stint teaching EFL in RoK. You should be aware that the South Korean government is drastically cutting the budget for Native English Teacher programs: all native English teachers have been cut from middle and high schools in Seoul; all NET positions were recently cut at the elementary school level in Mokpo; the NET budget in Busan has been cut; the budgets for EPIK, GEPIK and SMOE have been slashed; NET jobs that are funded directly from the local ministry are being slashed as well. Requirements are going up (degree specifically in English, education, or Linguistics, TESOL certification needed, MA in either English, education, or linguistics starting to be required in many places), and new, lower pay ceilings and lesser benefit packages are being instituted. With all the job cuts, those jobs that remain are in high demand from EFL teachers currently in Korea who are now scrambling for new jobs; it will be difficult for you to be competitive for the fewer positions from outside of the country, especially if your husband does not have an MA and TESOL certification; and those jobs that remain are paying less, and offering less vacation, then before. The EFL scene in Korea is not like it was when you left in 2010, and it is likely to get worse as the government transitions to a program of training and installing Korean English teachers in the classrooms (as has been the plan all along). In short, there is more competition, more requirements, and less pay and opportunity than when you and your husband were last there. Additionally, while I don't know if this was the case in 2010, it is the case going into 2013 that as a NET, you will hit a pay ceiling pretty fast, as the pay levels for experience in the new contacts top out pretty quickly (but your expenses related to child-rearing are not, alas, going to hit a ceiling, especially when you factor in saving for college).
To be honest, I think it's time for your husband to stop his self-centered refusal to look for jobs in the US (which is not to say that it's easy to find a teaching job here), as he gave up the right to think of his happiness first when he chose to father a child. I cannot imagine a husband wanting his wife to return to a place that made her physically ill and took 9 months to recover from, nor can I imagine taking a small child to a place that has a Yellow Dust season. Pollution has not gotten any better in Korea, and if you are unwilling to have your child immunized further, I certainly wouldn't taker him/her to live in a country that you acknowledge is both heavily polluted and hygienically challenged. Additionally, regarding your husband's level of job satisfaction: most of the cuts that will take place soonest have occurred in Seoul and other large cities like Busan; since there is immense and increasing competition for the fewer jobs that remain in these areas, that means that what foreign teacher jobs remain are tending to be in the more rural areas. If small-town living was making your husband unhappy in the States, I do not see that the current and future job market for EFL in Korea is going to help any in that regard.
If your husband is state-certified to teach science, then looking for a position in the International school system is certainly an option (which may be what you meant, now that I think about it). Again, though, given the recent and likely continuing cuts for NETs in the public schools (as well as increasing demands for university instructors to possess an MA), the competition for those jobs is going to be drastically higher than you remember from your previous experience. And you'll still have the yellow dust/pollution problem.
Check Dave's ESL cafe and Waygook.org for more info on the state of requirements and the job market in Korea.