O god! That is terrible. Please keep your cousin away from such movies if he gets influenced so easily. Children have this habit of imitating anything they see on screen.
Dowry is something that has been prevalent in the subcontinent for ages and it has nothing to do with one culture influencing other, it has been there in both the cultures since even before partition.
Heavy dresses, and heavy jewellery are not bad things, but I agree the pressure on parents to load the bride head to toe with gold should be avoided.
Dancing is not a bad thing, it is anything but bad/darkness/ignorance as mentioned by you.
You can't blame Bollywood or India for superstition, that again like dowry has been prevalent since even before partition.