I try to get something for you. Just my mind. Don't take it too serious though!
Mongoose are quite good predators, they are quite driven by their passion and are able to hunt down even snakes, they are quicker then them, they fight over minutes until the snake is so exhausted that it is a easy prey.
Seems for me like you are handling a issue regarding your family, that comes to the surface.
It's seems like something unavoidable, the snake as an animal standing symbolically for renewal/rebirth (because of the abillity to renew their skin) wouldn't get a mongoo down, or rarely(the chances are low). You are feeding the mongoose with a behavior you maybe don't recognize, because you didn't think anything bad and wanted to pet them.
Idk, if you find the "sense" between the lines.
You husband seems quite protective and ambitioned to protect the family, though you see it slightly different, than your husband he wants them to be dead(pragmatical) and you want to "cooperate"(communication) with them. Seems like you were both a bit different going along with unavoidable conflicts. If you find something that correlates with that, I suggest you to talk about it in a good minute. It was an example for how the family react in a situation where there is "irrational" conflict. Irrational conflict because the mongoose were biting even each other.
The thing with the fries I don't know seems totally individual, maybe something to do with your eating habits.
The thing with the cousin feels like a warning. I don't want to tell anything about your relatives. Maybe you are not voicing yourself clearly and some people tend to take advantage of you?
I feel the distraction thing and maybe taken advantage of if I hear of the bad food and baboons, baboons are apes with a strong masculinity to them, they hunt even animals down and are fighting for women and are aggressive. It seems like your brother in law is a person you trust or is good for you, that he warns you to overfeed the animals?
I think it was a friendly attempt to show you some conflicts, that are not yet present, though the potential is already there.
Sorry if it is regarding your family and provocative in some sense.
There is a good probability that this is just an interpretation and I'm just wrong, what humans are all the time