Biology: Symbiosis and surviving after being cut off

Dinoflagellates and giant clams or hermatypic coral is the one that springs to mind. The relationship is mutualistic, not parasitic. Giant clams feed without their Symbiodinium, as can corals. Symbiodinium can also survive without its host. (The problem with coral bleaching is that without the zooxanthellae to give them a boost, corals can't outgrow algae.)

I can't think of a relationship where both partners are getting measurable benefits from the relationship yet might be considered parasitic. I suppose the interaction between parasitic helminths and the human microbiome might fit, but that involves multiple species.

I don't think "feeding off emotions" is realistic biologically speaking. There's no evidence I know of that emotions are the result of any different kind of fuel/energy use than any other brain function. What would said parasite consume? Consuming fear/emotions is more in the fantasy realm than the biology realm.

There might be something in this angle:
10 parasites with the power to control their hosts' behaviour

Brood parasites are an interesting version.

The bacteria in your gut form part of the digestion process and in return we feed them.

While it may not be exactly what you're looking for, your OP brought to my mind the relationship between drongos and meerkats. It's not stated in this particular video, but most of the year (IIRC), meerkats like having drongos around because they provide warning against predators and don't cause any problems. The trickery and theft detailed in the video generally only happen when food is scarce, so there's a regular shift in their relationship from helpful to harmful.

Whether it's useful for your needs or not, it's a fun video to watch.

Lots of animals do that, rely on other animals' warning calls. Also many large animals tolerate small ones that eat parasites off their skin or clean their teeth.

Birds cleaning a croc's mouth.

Cleaning symbiosis

7 Symbiotic Wonders of the Aerial World

There are an ant species or two that keep leaf eaters off certain trees in exchange for sap.

Farming and ranching is a big category you might consider the symbiosis in. Dogs and humans of course, have lots of symbiotic relationships.

Look up scischow Portuguese man of war, it's very interesting.

What about a tapeworm and humans?

It's not symbiosis, but the parasite can exist within people for quite a long time, from what little I understand. Perhaps you can glean some inspiration from that.

Gut microbiomes are so complex & the populations so varied. A typical mammalian host can probably survive perfectly well without the presence of any one particular species in its gut community, doesn't know it was there and wouldn't notice its absence (much) but digestive health depends on a healthy gut biome, and many of the gut residents can survive outside the gut when necessary necessary for at least long enough to colonize a new host. Similarly for all the critters that live on a mammal's skin.

For "disrupted and have still survived", perhaps the cattle egret and the rhinoceros?

Cattle egrets will follow rhinos to feast on any small animals they flush out, and will alert the rhino if they see a predator. The rhino can survive without that warning, and the egret can look elsewhere for startled prey - they'll even follow tractors around on farms.

Personally I think the mutualism/parasitism between rhinos and oxpecker birds is more interesting, and a good example where one species wouldn't survive separation.

Yes, the birds remove insects from the rhino's skin, and warn of predators just like the egret. However. A completely healthy rhino provides very little food. An oxpecker will reopen healing wounds to get at larvae, ignore recently-attached ticks in favour of large and well-fed ones, and generally allow the rhino to suffer. Whether this is obligate mutualism or obligate parasitism for the oxpecker is yet to be concluded, but whichever it is, the bird wouldn't survive without its food source. (That would make the rhino a facultative mutualist or a host, depending.)

On behalf of readers with science backgrounds everywhere, THANK YOU for researching before you write!

This is totally not what you're after, but it's an interesting example of mutual cooperation: whalers and killer whales. I'm listening to a radio interview with the author of Killers in Eden, which is a non-fic about the community of Eden, NSW, and the pod of orcas that would drive humpbacks into Twofold Bay for the whalers to kill. Guided by the orcas, the whalers would even hunt at night.

There's no transcript, but you can listen to the podcast here.