dear mel, it is good you are reaching for insight and input. dealing with addiction in isolation pretty much fails.
on reading your story, i see a husband who loves his wife, a child who needs his family together, and an addict who knows she is an addict and who knows recovery but just isn't able this time to get back to it.
IMO, it sounds like a good situation for a professional intervention. that 's what i would suggest you look into, before you pursue divorce. she sounds like an ideal candidate for 30 or 60 day inpatient treatment because she has the motivation, beneath the addiction, to be a wife and mother. but she needs to get there.
with an intervention, she will be given a clear choice. what she then chooses will make things crystal clear for you and you will know then how to proceed for yourself.
do get support for your own emotional illness from living with an addict, mel. you deserve to feel better. a men's al-anon group could be a big help to you.
all the best, especially to your dear little boy.