What would your budget look like if your income wasn't included? I'd play around with a SAHM budget now and see how it feels. Bank the extra for DP on a house.
For your gifts savings, have you looked into any Christmas or holiday savings at local financial institutions? My local credit union pays 2% interest and it pays out mid October.
I second heygrey's suggestion re: playing around with the numbers. I would also try to live on just your husband's income for a few months before making the decision to SAH or not.
ETA: I am also impressed by your $50 clothing budget. I spend more than that and I think I like your clothes better (from what little I've seen). Teach me! Haha