Is a sick husband considered remiss in performing prayer if he delays the ritual bath (ghusl) from major ritual impurity (janabah) until the morning due to difficulty in movement?

There is no harm in sleeping in a state of ritual impurity (janabah) after performing the prayers, as long as you will wake up to perform ghusl (ritual bath) and pray on time. This is permissible, and it is recommended to perform wudu (ablution) for whoever wishes to sleep while in a state of ritual impurity.