Is a husband's action, where he divides overnight stays between his two wives, with two days for each, then delays one of them from returning from visiting her children for two or three weeks, and spends the remaining time with the other wife, considered just and lawful?

The husband is not obligated to compensate for the period following his wife's decision to return and her informing him of it, and his failure to accompany her. This is because, in principle, he is not obliged to provide for his pregnant wife if she travels with his permission for her needs. Therefore, there is no negligence on his part, and he is not required to compensate for that period.