Just a thought about the florinef dosing... my son was on twice that amount at your son’s age  (0.3 mg/daily).  He has been dropped to 0.1 mg daily over the last four months, but took that higher dose for his first seven months or so.  I think I read in an earlier post that too little florinef could compromise growth, so it may be worth asking about. 

Good luck with this.