Is the husband considered an oppressor and the wife oppressed in this situation, given the change in the husband's treatment, the decrease in his spending, and his coolness in the private relationship after his second marriage, despite his attempt to be just in terms of overnight stays and financial support?

The husband is not considered unjust if he is fair between his two wives in expenditure and lodging. However, he should not show his dislike for one of them. The wife should address the reasons for her husband's aversion, take care of herself, and adorn herself for him and be a good wife to him, as this may change his behavior towards her.