Introducing children and dogs?

Ok so my partners going to jail and I’m having his dog. He’s an English bulldog he’s only had him a few weeks but he’s 6 years old full pedigree the owners got rid of him which is how my partner ended up with him, I’m not to sure why they got rid of him thought. he seems relatively lovely, never gone for me, never been rough me, always gentle towards me, he’s went to nip my partner but only when he was hyper or on the bed(I think he has a thing for beds) but never me

Anyway, I was gonna get a stair gate at the bottom of my stairs so obviously he can’t go upstairs or on any beds, I have the space for him so it’s not like he’s going to be cooped up, I was just mainly wondering about what to do if any dog goes even a little bit of vicious? Also I know that dogs don’t really attack unless theyre provoked or want to be left alone.

I have an almost 1 and a half year old son who has met the dog once, petted him said aw and then left the dog alone, the dog just walked off and went to lye down. He does his own thing to be honest, he isn’t really bothered or hyper when people come. The dog is protective over me as I witnessed when someone tried to start on me my partner had to grab the dog cuz he would’ve went for them, I think he’d be protective over my son too especially because dogs normally are

I was just wondering how to introduce my child and dog properly and allow them to have a bond.

I would never leave my child alone with the dog as from experience with my old dog when he bit my cousin (he was a jack russel)and ever since then I’ve been a little weary and because animals have different minds to humans.