Hi Maddie,
Welcome to the forum. This is a great place to get information and there are many here who will want to help and offer advice. Three years ago, we suddenly found out I had stage 4 cancer on my tongue and it was possibly
HPV related. My wife felt guilty but it is hard to say exactly where my cancer came from (non-smoker, social drinker only). And, honestly, I didn't care other than wanting my wife to not feel guilty/responsible. Cancer is a fickle beast. We talked it through and eventually she relaxed and let go of that guilt.
From a medical perspective, the best advice I can offer it seems you already have, which is to jump on this situation and find a medical team that you trust. You may find writing in a journal will help. I did that every day for months. I ended up writing about all kinds of stuff - memories from childhood, current fears, doctor notes, etc. I enjoy going back and reading it occasionally. It gives me a reminder of how far we have come over these years.
Please let us know once you have more information about your husbands condition.
Stay safe and keep the faith,
Nels