I'm not sure specifically what 'Cap deage' means. It could be a very specific term, a misspelling, or something relatively unknown. It might be a proper name, a local term in a certain area or a very niche concept.
Spider - Man's light - hearted and quippy personality can provide a contrast to the more serious and stoic members of Team Cap. His sense of humor can lighten the mood during tense situations. For example, in a battle, he might crack a joke to ease the tension among the team members.
I don't have enough information to say exactly who Cap'n Kathy is. She could be an original character created by the fan fiction writer. Maybe she's a pirate - the 'cap'n' part could suggest that - who has some connection to the wizarding world of Harry Potter.
The cap man and monkey story is an interesting one. There was this cap man who was traveling around selling his caps. He reached a place near a forest and decided to take a rest under a tree. While he was sleeping, the monkeys in the tree noticed the caps. They climbed down, grabbed the caps, and went back up the tree. When the man woke up, he was confused at first, then saw the monkeys with his caps. He was worried as those caps were his livelihood. But then he remembered that monkeys often mimic human actions. So he took off his own cap and tossed it. The monkeys, being the imitators they are, did the same with the caps they had taken, and the cap man got his caps back.
Cap would be shocked at first. He trusts his comrades, and for the Clint team to betray him would be unexpected. He would likely feel a sense of betrayal and anger. He might start by trying to isolate the situation, to keep the knowledge of the betrayal from causing too much unrest in the Avengers. Then he would try to find a way to stop the Clint team from causing more harm, whether through negotiation or combat.
In a Christmas story, the vintage red hunting cap could play a significant role in a family tradition. Maybe it was passed down through generations and every Christmas, the person who wears it has to perform a special task like lighting the Christmas candles or reading a particular Christmas story. This way, the cap becomes an important part of the family's Christmas heritage and the story could revolve around the memories and emotions associated with it.