My friend has sleep apnea, everything we do revolves around his needs but he makes no effort to improve his sleep. Could this also be a control issue?

Perhaps. You haven't given any information about what steps you have taken to deal with the problem. Is your friend using a CPAP machine or an oral sleep apnea device?
Yes. Sleep apnea is a potentially a very serious disease. The only true potential cure is weight loss. In a morbidly obese person bariatric surgery is potentially curative. Ultimately i agree that this person may at times let their disease define them andvd allow them to demand preferrential treatment. Remember that ultimately it is their disease and not yours and they need to take some responsibility.