Have you found a favorite cream yet for your son? When Laura was a baby, I was initially advised (and this is what I did) to not bathe her but to cream her with Eucerin (the heaviest moisturizer that was available then) every 4 hours. This kept Laura reasonably comfortable--and she was a collodian baby with severe lamellar ichthyosis.
Now, of course, most people recognize that bathing is an important addition to the treatment program, but creaming immediately after to seal in the moisture, remains a critically important part of the process. Also, there are alot more suitable creams than just Eucerin available now.
I'm sure that some of the other mom's that read this board will respond to you soon. Laura's 31 now, so this was awhile ago for me. But, if you contact FIRST, they could help put you in touch with other mom's facing the same problems now (or moms that have been through this more recently). You can reach FIRST at 215-631-1411.
FIRST can also help you get in contact with a dermatologist who is familiar with ichthyosis. Seeing a doctor who is familiar with ichthyosis is very important in order to get the best medical advice. Most doctors have never seen ichthyosis because it is so rare. All doctors of course do their very best to provide you with their best advice. But really, the best thing for you and your baby is to deal with one that is familiar with ichthyosis already.
I hope this helps. My heart aches for you and your baby. I'll keep you in my thoughts.