{{{Hugs}}} for watching him go through that.
Not sure if you know this but many if not most lo's do outgrow a true dairy allergy. I don't remember the numbers or stats exactly but something like 95% by the age of 3. I'm holding on to that like a lifeline right now, and E HAS gotten a bit better with dairy as most do.
I strongly recommend you get as much support as you can for eliminating foods and be candid explaining to people especially around the holidays so you know what you can eat.
Still here offering whatever support you need