Is it obligatory for the husband to make the intention for Hajj, as his pregnant wife did? And what should they do if they are interrupted from performing the rituals due to an emergency trip to the hospital, whether they are able to complete the remaining rituals or have missed them all?

It is permissible for spouses to stipulate a condition when entering ihram for Hajj or 'Umrah. If they are able to stand at 'Arafah, even for a moment, before the dawn of the Day of Nahr, then they have attained Hajj. As for Tawaf al-Ifadah and Sa'i (for those performing Tamattu' or those who did not perform Sa'i upon arrival), these are pillars that cannot be compensated for by a sacrifice (dam), and they can be delayed until the excuse is removed.

Regarding the rest of the Hajj rituals (such as spending the night in Muzdalifah, stoning the jamarat, spending the nights in Mina, and Tawaf al-Wada') these are obligations. If it is possible to perform them, then it is obligatory to do so. If they are left due to an excuse, there is no sin, but a sacrifice (hady) is required for leaving each of them.

If standing at 'Arafah becomes impossible due to illness or similar reasons, each of them is released from ihram and no fidyah is required.