Hi and welcome to the Chiari forum.
I am so sorry u have a little one suffering.
It does sound like ur child may have a few other issues...chiari can cause sleep issues and sleep apnea, so do have that checked.
With the idiopathic hydrocephalus that comes with the benign macrocrania may also bring with it other health issues that most with chiari are not faced with.
The eating and sensory issues can be a factor in children with GERD....and that can be y there is congestion issues as well.Then there is sines issues we all tend to get too.
I would suggest u find a a Dr well experienced with chiari and macrocrania benign or not to help guide u.....
U need to know if ur child has a CSF obstruction, a syrinx, tethered cord, and the other related conditions I mentioned above .
Here is a list of our members Drs- this list is not a referral, it is only a means for u to start ur research Drs....see a few and compare them and go with ur gut as to whom u feel is best for ur child.
Please keep us posted on ur child's progress and ur Dr search.