Yes, the Winter Soldier comic is considered canon within the Marvel Comics universe. It plays an important role in shaping the character's story and continuity.
The Winter Soldier's age in the comic varies depending on the specific storyline and continuity. But typically, he's depicted as being in his 30s or 40s.
He could interact in a protective way. For example, if it's a small animal like a rabbit, he might build a safe place for it. His military training would make him good at creating a secure environment.
For 'dark winter soldier fanfiction', Falcon could be an interesting character to pair with the Winter Soldier. Falcon has his own set of skills and a strong moral compass. He could help the Winter Soldier navigate the modern world and his newfound freedom. Also, Scarlet Witch would be a fascinating pairing. She could potentially help him deal with his traumatic memories through her powers. And Bucky could also be paired with Doctor Strange. Strange could use his magic to help Bucky understand and control the dark forces within him.