Explanation of a Hadith

Q: Never does anybody leave something for the sake of Allah but Allah will give him something better in exchange.

What is the Meaning of the above? Does it mean that If one leaves his family and goes to jamat or other deeni cause then Allah will reward with some better reward? Or does it mean that if one leaves out haraam act or food then one will receive better than that for the sacrifice one makes? Please can you clarify?

Premarital contact

Q: I am engaged and my in-laws are much wealthier than my family. I talk to my fiance on text messages. I observe the girl is rich and her parents fullfil all her wishes. She uses all expensive items which I know I cannot afford. My fiance's life routine is very different and my routine is very different. I told my parents about the routine they said girl will adjust herself after marriage. When my parents were looking for a girl for me, they never asked me what kind of girl I wanted to be my wife, what kind of in-laws etc. My family just fixed my engagement and showed me the girl. When I spoke her on Messages, I was disappointed. I cannot say to my parents that I don't want to merry her because they are very happy with this relationship, and this is not good for the girl also to break the engagement. Please help me I am tense.

A child's vomit

Q: I was talking to my brother about my situation regarding my nephew's vomit and he told me that if a vomit which is more than mouthful falls on anything that makes it impure if it is more than the inner palm circle. If the vomit was less than moutfull and the baby vomited 100 times on the same matress and no matter how many stains their are on the mattress it would not be considered impure. Is this true?