My ex is not wanting to give me my things or our son’s things the only way I can get our stuff is…

My ex is not wanting to give me my things or our son’s things the only way I can get our stuff is when he goes to take his sister to the airport tomorrow at 6am because his brother has agreed to help me get everything but it has to be when he leaves and the airport is only 30 minutes away so I’m just hoping I can get everything within that time frame. On top of that his mom told me I wasn’t allowed to take anything she bought my son and I said okay. She only bought the stroller and car seat so now I have to go buy a new set before my son gets here. I’m honestly just ready for this to be over I just want my stuff and to put this behind me for now until my son comes all this running around is just so uncomfortable for me I can barely walk up and down the stairs without needing a break. And the thing is I have been remaining cordial and respectful to his family and everyone is upset with me for not staying the only one who is understanding of where I’m coming from is his brother. He even offered to give me the stroller and carseat set he bought his son and take the one his mom is keeping from me. I just feel bad for how this will ruin things between him and his family. I don’t understand why they’re mad that I’m leaving when they barely wanted me there to begin with.