The emotions thing is impossible to answer from what we know now. They can probably feel disappointment (at a missed opportunity or an escaped victim) or anger (maybe at strong opposition), but I'd bet against love and sorrow as we understand them.
Although there are many creatures that are changed from their predatory ways in fiction, demons appear to be born from some kind of suffering or pain itself. At their core, their consciousness is stimulated into being by their malicious intent. I don't think that can be changed, lest the demon willingly return to a primitive state of non-sentience.
As far as the demon of secrets goes, I'm really looking forward to that story. We know so little of it. But I don't think its patterns are all that different from other demons in truth. Swain is said to have made a Faustian bargain with the demon, which fits what we know of other demons. The demon may acquire and dispense secrets in exchange for something from its victims, but Swain evidently bet everything and then somehow defeated it. I don't know if the demon itself is on Swain, or still in the Immortal Bastion. If it's on Swain, it's probably nearly dead/in a coma, but if it's in the Immortal Bastion, then it might just be heavily subdued. Swain probably has to change nothing; he won and the demon's power is essentially his own now. It has no power over him.