Doubting the Imaan of people

Q: In America there are a lot of people that are converting to Islam. Sometimes I get the doubt that some of them are just acting like they converted but they are actually munafiq like there were munafiqeen in the time of the Nabi (Sallallahu Alaihi Wasallam). Is it wrong to doubt the iman of a Muslim if he is a Muslim zaahiran?

Giving zakaat to one's brother

Q: My younger brother is jobless and have no source of income at all. He got married and now expecting baby this month (Insha Allah). Since he is going to have addition in his family and it will be hard for him to bear expanses for himself, wife and newborn. Can I give him Zakaat money so he can manage his living expenses?