As hard as it is, I would try to take yourself out of this situation, meaning become more objective and less subjective. Your husband is doing exactly what he has been supporting you NOT to do, that is, turning to alcohol for comfort and solace during a difficult time. While I suppose that is understandable, you should not make the mistake of using him as your example.
All human beings are weak and will stumble and fail. Your HP needs to be your guide, not the actions or subtractions of other human beings. You can support your dh in grief, while at the same time not condoning his drinking, (and driving!?) It sounds to me as though some grief counseling is in order for him - you could offer to go together and while there bring up your new sobriety and the fact that his drinking is not encouraging you to stay sober.
Your mutual suffering can bring you closer as a family as long as you do not take your dh's suffering to be an excuse for you to misbehave. His reaction to his father's passing is his business, not yours. Your business is to maintain sobriety at all costs.