You bear the same child support as he does, half each. If you don't give alimony, you can sue him in court. If he still refuses to give it after the court decides or mediates, you can apply to the court for enforcement. As for the house you mentioned, it depends on the resettlement policy. You can ask the demolition and resettlement office. If you have your share, it will be easy. If you three have resettlement houses, he will give you money if he doesn't give you a house. If you bring a lawsuit directly to the court and fail to perform the court's judgment, ruling or mediation, you may apply for compulsory execution. It is recommended to consult a local lawyer.
You said his house was transferred to his sister. From a legal point of view, it should be considered as a free gift. On this premise, the property right of the house belongs to his sister.
You say you are weak, but I disagree. Everyone is equal before the law, and we should use legal weapons to safeguard our legitimate rights and interests.
I hope my answer can help you!