You are not petty at all for feeling this way! This is pretty stressful behavior to deal with and props to you for sticking it out for this long. I believe having a serious talk is very much needed and if need be, see a therapist that could mediate that discussion. Also, there are many resources online as well that pertain to your position. I believe there are programs like Al Anon for loved ones of those addicted to other substances.
Also, instead of gum, he could always try patches. The nicotine can greatly influence moods and outbursts. I know this from personal experience. It is scary to see how much of a rage lack of nicotine can cause.
Above all, please take care of yourself and if things go too far or continue to go downhill, put yourself first.