Can I give spinal stenosis to my husband?

No. Spinal stenosis is not an infection - it is not contagious or transmissible from one person to the next.
No. Spinal stenosis does run in families. It has a genetic basis. It comes from your ancestors, not from your spouse.
No. Spinal stenosis is not a transmittable condition so you do not have to fear. It may be more due to his activities, history of accidents, or his genetics or a combination of all 3.
You can help! While directly not, unless you overfeed him. Abdominal obesity will accentuate lumbar lordosis, not support the torso properl y with taught abdominal muscles, leaving more weight to carried by the spine. But no it is not directly transmissible!
No. Spinal stenosis is narrowing of the spinal canal, leading to pressure on the nerves within the spine. It's primary cause is arthritic change. Thus, it is cannot be transmitted to others.