calming signals

I read your other thread as well, and you have a love and connection with animals, this is an automatic connection. Do you talk to him a lot, always acknowledge him, these are things that make him trust you.
You mentioned your daughter has a Sheltie, are there other animals in the home as well? The Sheltie may very well be a large part of why he doesn't feel comfortable in her room. When cats bond, they sleep together, this is the sign of complete trust and acceptance.
Cats do have signals, but they are not always as obvious as dogs. Their main physical display of what they are feeling is through their tails and ears. When a tail is straight up and twitching it means they are excited to see you, when they whip it back and forth it means they are irritated and warning you they may bat, bite, or leave PO'd.... The ears usually work with the tail, perked up is curiosity or attentive, slightly tilted to the side is frustration or unease, flattening their ears is defensive, extremely irritated, usually hissing as well and either going to attack or show submissive behavior.
I hope this helps a little. There are threads on TCS that give links and much more information about this. You can do a search in the "search" bar at the top of the page.
I can see why this kitty loves you! You want the best for him, and he knows it! Cats are very smart, there is always a why behind everything they do.......

i can only speak about *my* cats, not all cats. if penny doesn't want to be bothered by daisy, she will often hold up a soft paw. it looks like sign language i.e. "talk to the paw" and she will add a snooty look to her face. a lot of times they "greet" each other nose to nose. i think they're saying hi. (i live in a 2-cat household, so things might be more complex in a home with a greater number of cats)

Aw, that's so cute, I think he just likes you! You must be his mommy figure.

A coworker of mine was telling me that her cat HAS to hold her hand. She said wherever she goes, her cat walks over by her side and slides his paw under her hand. How sweet is that?

I can't think of any calming signals as you described them but they do have many warning signals that give when they don't want to play or just want to be left alone. The paw in the air is definitely one of them, but the tail twitching is the main thing I look for. They start wacking it around hard when they're annoyed or want to be left alone. This is typically accompanied by them facing away from you, but not always.

Also, slow blinking of the eyelids and sitting with paws tucked under. At least that's my interpretation

An eye blink is a sign of greeting with cats. When they do it, they are telling you that they accept you as one of the "pride".

When I watch the positive interactions within my cats, I notice a lot of head bumps - either they'll bonk foreheads together, or will rub their faces up against each other. They also mutual groom, which always seems to relax them. If they aren't in piles together, they will reach out and touch each other - I have some that just like to lay next to me with a paw reached out to touch me.

I've noticed something here.

Regarding the tail whipping left to right. i've read that this is actually a hunting method. they sit perfectlly still, flipping their tail left to right to get the attention of the target. when they look at the tail, the cat attacks.

Don't know how true that is, but I know one thing, my cats DO NOT adhere to the standard statements about tail whipping etc.

Wilbur likes to bat me with his tail. if I pick him up and hold him close, he whips his tail to the right, then smacks it back at me. he's not mad, he's just telling me he's happy (at least that's what I think).

Tinker also doesn't follow the normal path. her tail stands straight up and twitches if she's really scared. when she's excited to see me, she wags it left to right at about medium speed, but it's very pronounced.

I think the general explanations work, but i also think each cat has his own ideas.

I know my cats very well, i talk to them like they're people . I have a really good connection. iv'e learned that I can call tinker over to me without saying a word. if I look at her, softly close my eyes, then open them, and look back to the tv or whatever, she comes over to me. But calling her doesn't work. I know cats use that open/close eyes thing as a sign of peace and content. but I just think there are big variations because they evolve their communication based on your response to them