Hi Vonz,
Welcome to the site, and I'm glad you posted and introduced yourself. I still remember how weird I felt the first time I posted in the forum. All my deeply personal baggage made public for all to see.
I highly recommend Lesson 5 to the right ---------------> about raising resilient kids when one parent has BPD. Especially the part about validation. You probably want to get your head around Lesson 6, too, on parental alienation. That tends to go with BPD and coparenting. It's great that your child is young. Validating his feelings young in life will go a long way. He won't get much in the way of validation from his BPD mom, so you're it. You're the one who is going to help him figure out that he has a self separate from his mom. Many BPD mothers have an unstable sense of self, and their kids are extensions of them, which can be very frightening and confusing for a child, who is hardwired to be dependent on this all-powerful figure.
If nothing else, get a copy of the Power of Validation and practice the skills in there until you really get it. You can start with little kids, and it works right away. The challenge is that sometimes it's hard to know if you're doing it right, and in particular, doing it authentically.
LnL