You have recounted almost exactly the story of my mother, my former two cats and myself. The saga in shortened form goes like this...
I adopted a cat that was abused in a kitty mill. She became my baby and lived happily with me alone in our apartment until my ex-fiance decided to give me another cat as a "present". This cat was a barn cat(unusually big, tempermental, and very unpredictible) that had been weened too soon from it's mother. Needless to say, my ex knew what he was doing...this was not a gift of endearment. We were seeing the writing on the wall that there wasn't going to be a wedding and he thought it would be payback to give me this very cute but troubled cat.
My first cat was declawed and had no defenses. Needless to say she was livid that she was being forced to live with this crazy barn kitten that still had her claws. Barn cat never liked me. She tore up my furniture, clothes, and carpet. She used to poop in my purse all the time (real interesting responses and reactions when I pulled out the billfold in public or left purse next to desk at work!!)Back to the cats...kitty mill kitty always was very devoted and loving. Unfortunately, things got violent...so much so I thought I had to get rid of them both. My mother wouldn't let me, and she agreed to keep them both. Daily, they'd get on their haunches and box like kangaroos...no kidding. They'd hit each other so hard it sounded like someone pounding a wooden box really hard with a club. The declawed one would use her hind feet to tear up the barn cat (B.C. was twice as big and round as the Kitty-Mill cat) They too would avoid each other and "mark" their territory (KM never pooed in the house until the turf wars started) and if either crossed the smelly line, watch out! Lucky for them, mom didn't mind the chaos.
A year later, I wound up moving back home with my parents until my wedding (got rid of evil ex and was going to now marry mr. dreamy). Mom had just about had enough of the kickboxing and was ready to send them back to me and my soon to be new DH. But he's allergic to cats...AND he already had a big hunting dog.
The minute I came home after not seeing either of cat for months, they both HISSED at me. They both hated my guts. They wouldn't let me pet them. They'd hide under tables etc. As for my fiance, now husband, they had it in for him. Somehow they knew he was allergic to cats and weren't coming home with us. They hiss at him, hop on his head, roll in his coats, etc.
They didn't get better when we had kids. I too worried about the cats scratching the babies' eyes out (mom watched them when I worked). They didn't like the kids either...but for different reasons. They were frightened by the kids when they were toddlers and were more curious aboutn the kids than anything. They will let the kids pet them, but only real quick and they take off and leave them alone. As for me and hubby, they hiss and will bite and scratch.
My conclusion...cats bond and obviously can feel betrayed and carry a grudge. I'm not saying they'll always resent your son, but they probably feel abandoned. Like any animal, they probably smell different smells on him, and pick up maybe even a change in demeanor as he's now probably focused on different things and not so attentive as before.
I'm certain my cats don't like smelling Labradore Retriever smells...and I know my kitty mill went through ALOT before I got her and probably has alot of trust/abandonment issues.
As for the questions about the baby, I don't trust any animals with young children. I say use caution. If the cat hasn't actually hurt anyone, the cat probably won't hurt the baby if you keep them a good distance from each other and never leave them alone together...which it sounds like you're doing already. However, if the cat has attacked, bit, or scratched before you have a good reason to be worried, and I wouldn't hesitate to consider finding it another home. With that kind of uncertainty, it isn't worth putting the baby at risk for serious harm.
As for declawing, you will be hard pressed to find any vets who will do that. It's pretty much concensus that declawing causes serious damage to the cat's paws and can in many cases cause crippling and undue permanent pain (as I've been told). The other argument against it is if the cat were a house cat that got loose, they'd have no way to defend themselves.
There are still some vets who will do it, but they're probably not really declawing as much as they are using a newer method where the nails are somehow cauterized (sp?) so they don't retract (as I've also been told so don't quote me).
There are some non-surgical solutions, including having your cat's nails encapsulated in rubber tips. You can have a vet do this, or by the caps and put them on yourself. Check out www.drsfosterandsmith.com.
Hope I didn't ramble too much...probably more than you wanted to know. Tell your son to hang in there. This is tough stuff.