If you have been together for a year, I am guessing that you have had some time to talk about the future, and how you are going to deal with parenting together. It is very hard when you are at such different stages of experience.
Presumably your dp has done some reading, but I would highly recommend the following books, if he hasn't already read them:
Steve Biddulph - "raising boys" is an absolute must, IMO, for anyone with sons/stepsons. (I have 2 boys and found it extremely helpful).
Jo Douglas and Naomi Richman - "coping with small children". It is aimed at parents of babies and toddlers, but will give your dp basic insight into how toddlers develop, as he has missed this stage with your ds.
There are other books that are frequently recommended by mnetters - one is called something like "how to talk so children will listen" - someone will come along and clarify, I am sure.
Parenting is the most challenging and difficult job there is, and frequently seems to be the one for which we are least prepared. There is a lot of information out there - libraries usually have a good stock of information, and will order books for you.
You can get information on parenting classes from health visitors, school, and probably through sure start, if there is a scheme in your area.
I also think a basic first aid course is essential for anyone who is going to be looking after a child - including parents.
Having the benefit of the knowledge and experience from books and classes can build confidence, and will hopefully make the whole situation less daunting.