Hello there and firstly very sorry to hear of your distress as such an awfal time. Your warning is very good advise - I could tell you many a story of people who forget to mention tablets they are taking - often because they have been taking them so long they do not consider themselves ill- and understandably insurance companies do not cover if a full medical history is not disclosed.
However, Son Dureta do have a number of excellent public relations staff who speak english and they can provide all the info you need from the Drs. as to the condition of your husband and future options. Son Dureta is the best hospital in the Baleares so your husband is in very good hands - the private hospitals are best for convenience not for their standard of treatment.
I would imagine that your insurance company will still assist you as much as possible and to be fair they will have all the contacts needed for arranging flights home and assistance during the flight when you come to that time. However they are likely to want you to pay for the services if they are unwilling to cover his treatment.
I am not sure if you are religious but there is a lovely friendly English vicar in Palma, close to Son Dureta, who visited a client of mine a few years ago when her family had to return to UK. His name is Robert Ellis - 971 737279 and he may be willing to pop along to cheer up your husband.
I imagine that your husband is in Intensive Care if you are unable to stay in the hospital, when he is back on a normal ward, it would normally be possibly for you to stay the night there, all be it in an armchair, but this would keep the costs of you being in Palma down.
Wishing your husband a speedy recovery and I hope you find plenty of assistance.