1. By itself, the phrase "Sharing is caring and all" is not a great sentence. However there is a grammar structure being used here "..... and all, but .....", so the full sentence sounds a lot better.
"Sharing is caring" is a 'saying' in English. You can think of it as something like a "chéngyŭ" in English.
The grammar structure "..... and all, but ....." means that the person knows this saying, but he or she is ignoring the saying.
The first part is the saying, the "and all" means the person is aware of it, "but" is a contradiction, and the last part is the reason for ignoring the saying.
So Vince is correct.
2. Yes, metaphor. It makes the intended action very strong. He's not just suing them, he's suing the pants off them! He wants to "bleed them dry". He probably wants to sue for a lot of money.
3. A "Go-to {option}" means that it's the person's favourite {option}. If there are multiple options, it is their first preference. Sometimes out of impulse, or sometimes because it's the best option. When something happens, it is the first option that the person will think of, and usually they will choose that option (unless they see another option which fits much better in that situation).
"Go-to" is usually used in these ways: "It's the best person to deal with a particular problem or do a particular thing, or the best place to get a particular thing or service"
It is also possible to use it in this way: "go-to threat", but it's less common.
So the words "go-to threat" mean it's that person's typical threat. It's the threat they will usually "go to" when they need to find a threat.