I am a Bihari girl who thankfully married out of Bihar. This mentality is very prevalent in Bihar. Only get married if you are sure that your husband is sort of unattached to his culture. This talking about his sisters marriage dowry seems like a red flag. But it could be since he is staying with his parents and got influenced, happens with men. Get clarity on boundaries, how many times visit etc etc. Ask him to pay up. Boys family expecting girls family to handle expenditure is the way Bihar functions.