Hi, and welcome,
Yes, information is your friend. Seeing a lawyer doesn't obligate you to do anything, but it might give you an idea of what your rights and obligations might be. He would undoubtedly have to support his child, which includes helping to pay for day care, therapy, and anything else the child needs (food, clothes, a place to live, etc.). I also strongly suggest you find an Al-Anon meeting and start with that. You are feeling (understandably) overwhelmed, and because Al-Anon focuses on getting you healthy after living with the insanity that goes along with alcoholism, it will help you clear your head so you can make good choices.
Believe me, the logistics of separation and divorce, as well as being a single parent, can be learned. You can gather some good friends around you--including those you will meet in Al-Anon (who will understand the way no one else possibly could)--who can give you advice and help when you need it.
You don't have to decide anything this minute. Start taking some steps to take care of yourself and your and your son's future and eventually things will become clearer.