There are two sub-types of lung cancer: Stage II A and Stage II B. 
With Stage II A, a tumor measures more than 5cm but less than 7 cm and has not spread to the lymph nodes. Alternately, the tumor may be less than 5 cm and has spread to lymph nodes. 
With State II B, a tumor is more than 5 cm but less than 7 cm and has spread to the lymph nodes. Or, the tumor could be larger than 7 cm, but has not spread to the lymph nodes, though it may have reached nearby lung structures. 
As far as the seriousness of your husband's illness, there a number of factors to take into consideration. His age, general health, and his response to treatment will play a major role in what to expect.  He has a better chance of recovery if he follows his doctor's advice and takes care of his body. Good luck to the both of you!