Wife cooking for her in-laws

Q: My married son and his wife says that there is no duty of the daughter in law to make food for the father in law, mother in law and brother/sister in laws. Even it is not her duty to make food for her husband, rather it is the duty of the husband to provide food for his wife and they claim that this is the law of shariah. My question is, do they get married only to fulfill their sexual needs and bear children? What does shariah say in this regard?

Swallowing the moisture on one's lips after wudhu while fasting

Q: The moisture left on my lips from washing my face/mouth during wudu, is this safe to be licked and ingested when fasting? Usually after I wiped my lips in wudu, I have to spit and then let my lips air dry and/or wipe with a tissue until dry. Today after wudu, the majority of my lips were dry but in the corner of my lips I felt a coolness, which may indicate that there is still moisture from wudu left. I licked that area. So now I’m just wondering if my fast is valid.