Sorry to hear you and your husband have joined the Amyloidosis family. But it is a family and you get a lot of answers, support and you'll get encouragement as to what kind of questions to ask you doctor.
With the chemo, you'll just have to see how he responds. After the first treatment or two, you'll see patterns and they stay pretty consistent. All depends on his treatment regime. I was on CyBorD where the D is a steroid that makes you real jumpy the night of the treatment. The nurses joked with my wife, make sure you give him a list chores for the evening. The next two days were generally fine, and then on day 3, it hit me, nausea, fatigued, irritable, but nothing that wasn't manageable. Some times I could make it to work the 3rd day after treatment, other times I just turned around and went home. So, basically, I was down 2 days of 7 (the day of the treatment, and then 3 days later). I'm 57 and started this journey at 54, so youth is on your husband's side.
The tricks are to stay active, but don't overexert yourself as if you were healthy. Sleep when you need to. And stay properly hydrated. That's a unique balance for everyone. Ask you doctor for ques as to what's hydrated. Basically if you're licking your lips and urine is yellow, slowly drink a glass of water. Also, with the nausea, you'll hear stay ahead of the nausea because once it hits it too late. You'll get a feel for it after the first couple of treatments. The doctors should have a medication they can recommend if needed.
My doctor started me at the recommended does based on body mass, and after the first cycle (four weeks, three on/one off), increased it since I tolerated it well and the hematological response was good. Early on I was a candidate for a Stem Cell Transplant, so he wanted to be aggressive in getting the Free Light Chains down.
And the most important thing I can tell you is to keep a daily diary and just jot down "it was a good day" or list symptoms. This helps you in discussions with your doctor, and allows you and your husband to better track the cycle. Also, talk to your doctor about side effects. Let him know how your husband is feeling. Again everyone responds differently and he may have to alter the treatment regime. And finally, make sure to let you doctor know about any and all supplements and prescriptions. And ask what he can or should not eat while on certain medications and treatments.
If your husband is put on the CyBorD treatment regime, the Bor stands for Bortezomib (aka Velcade). It was a very important part of my regime, but it did make me very sensitive to extreme heat and direct sunlight. My treatments started in the late Fall and went through winter and following a Stem Cell Transplant in February, I had to do a few more cycles of Velcade in June and July. Then one day in the field I almost passed out. It was a side-effect of the Velcade that we didn't notice or think about early on due to it being winter time. But I had it in my notes for my next visit and we discussed it.