George,
I know from your
previous post that this diagnosis is what you feared. Clearly, getting the MDS diagnosis is still a huge shock, and you and your partner must be reeling. Many of us have had this shock, but everyone reacts in their own way and copes (or not) in their own way.
I don't know what will help you the most, but I can tell you what helped me: learning all I could about the disease and its treatments, and doing my utmost to work with my wife and her doctor to take care of her. There are more choices of treatment now than ever before and success rates climb every year so I see many reasons for optimism.
As to the cause of his MDS, most patients don't get an answer to that question. Unless he had known exposures to toxins or previous chemotherapy, it may the result of random genetic mutations that we all experience throughout life, which are usually benign but sometimes result in disease.
The best suggestions I have for your partner are to rely on doctors and a treatment center that have lots of experience with MDS and to work with the doctor (and you) as a full partner in his own care. I think that patients who help with the decision-making and who understand what's happening to them, from both the disease and from the treatments, make their own luck -- and that it makes a difference.
The best suggestion I have for you is to use all the support available to you from your family and friends, online sites like this one, community services in your neighborhood, and your partner's treatment center. That includes getting professional consultations, if they will help, to address the emotional issues that patients and caregivers all face in some form. You need to find what helps you cope so you'll be able to help your partner. No matter how much support you get from people over the Internet who have been in a similar situation, it's not a substitute for face-to-face help.
How are your partner's spirits? Please keep us posted.