Whatever you want.
Technically they are not at all related to you as your only related to your cousins husband by marriage. But to your cousin you could tecnically classify him as her nephew by marriage
Your first cousin's cousin could be your, your siblings or one of your other cousins. The precise relationship depends on how that cousin is related to your first cousin.On the other hand, every one of your cousins has cousins who are related to them through their parent who is not a sibling of your parent. Thoee cousins are not related to you at all.
Technically, yes. To be specific, you are second cousins.
You are related to some of your cousin's cousins, and not to others. If you have an ancestor in common, you are related. If you do not can a common ancestor somewhere, then you are not related.
You are not related to your husband's cousins.
Probably not. You are technically only family if you share a common ancestor. If you do share a common ancestor, then they will be your 2nd cousin as well. It is not likely (but possible) that you are related to them.
The first cousin of your dad's first cousin is also your your dad's first cousin or is not related to him or to you. The children of two first cousins are second cousins to each other. So the son of the first cousin of your dad's first cousin is either your second cousin, or is not related to you at all.
Your cousin's wife is not related to you, so her cousins is not related to you unless she has some family connection to you besides being the wife of your cousin.
Your cousin can have many cousins who are not your cousins. If you and your cousin are related through her father, then all her cousins who are are related to her through her mother are not your cousins.
Your cousin's cousin may be you, your siblings, your cousin, or may not be related to you at all. Your cousin is related to you by being descended from the brother or sister of your parent, grandparent, great grandparent, etc. Your cousin will have cousins who are also descended from those people, but will also have cousins on the other side of her family who have no relationship with you.
You and your second cousin's children are second cousins, once removed. Your children and your second cousin's children are third cousins.
You and your first cousin's children are first cousins once removed. Your children are their second cousins.