I can't agree more with the comments here, especially not second guessing. It just drains energy, and accomplishes little. Just take it as a learning experience, and readjust plans as new info comes in.
I was in your shoes somewhat. I found my cervical lymph node tumor myself while rubbing my neck, saw my primary doctor, and had it removed by a general surgeon, just one week later. Never saw any ENT, Oncologist, or had any head or neck scans, just a chest x-ray.
So when it biopsied as SCC, I went to a cancer center, had a PET /CT scan, and they referred me to a ENT.
The first thing the ENT said, after shaking his head, is that I did so much out of order. But he didn't spank me too badly, he came up with a referral to an ENT Oncologist.
But from there onward, I just made sure to make my appointments ASAP, get insurance authorizations, get copies of my reports and images, and document and understand where I stood at a given time.
In other words, devote my energy and time to what is in my control.
If there are any residual cancer cells left from the lymph removal, then I will have to have faith that the rads and chemo I just started, cleans that up.
I know those t-shirts and mugs are a little corny, but it's so true with this unique cancer, "Keep calm, and carry on".
You are on here getting advice, you are being a caregiver, getting information to help make good decisions, so you are on a good path. Have faith, that anything that happened that wasn't optimal, will be compensated for by current and future treatments.
All the best to you and your husband.