Welcome to the wonderful world of chihuahuas!
My Zorro, almost 4 years old, also doesn't like to be messed with when he's sleepy. He growls and fusses when I move him while we're sleeping. He also sleeps with my husband and me; well to be accurate he sleeps with me.
My husband moves too much for Zorro, and if he's being disturbed too much he'll do that growling thing. If you actually wake him up he'll snort or kinda grunt at you and move somewhere else to go back to sleep. He's VERY opinionated.
As for this being an aggressive behavior I would say no. Well with Zorro, it's just his way of saying, "Don't do that!" Could be that your baby is that way too. Zorro also makes that same sound when he's playing/wrestling with my husband. He wrestles with Brian, but only wants to snuggle and kiss on me. It's like Brian's his playmate, and I'm his snuggle partner. And I suppose Zorro would say that we all know you don't mix those two together. LOL.
As for protective of you with company, I have a little girl, Peca, who belongs only to me. She's Zorro's daughter. She refuses to even let my husband touch her unless she's sitting on my lap. She gets all anxious when he tries to pick her up.
And as far as company, she's like that just isn't happening! I've gotten to where I now put her in "Our room" as I call it so she can snuggle in our bed and smell me. She sleeps with my husband and me too, and just freaks out if there's a door closed between her and me. She even has to go to little girl's room with me. I just can't stand to hear her cry and carry on.
I guess you could say I spoil my babies in the worst way ever.

I told Brian that now that I'm working again (I was out of work due to health issues for a while) my main goal was to get a fence for my "children." And I buy their favorite dog food for them, because they deserve it you know. We even have doggie doors for them so they can go out and come in as they please. I guess we're just "dog" people, but maybe we're "pet" people cause we have two cats too. Oh well....all these words to say I don't think your baby is abnormal unless mine is too.
I hope you enjoy many years of bliss and love with your young one!
In Christ,
Crys