Hello, I am so sorry that this has happened to both your Dad and You. It is scary, but take some deep breaths. You will get through this.
There are many here who will jump in with similar tales. Unfortunately, this is becoming increasingly common. It is also a treatable cancer. This is most likely an HPV positive cancer and as such has a survivor advantage. These cancers respond more readily to current treatment of concurrent ( at the same time) chemotherapy and radiotherapy.
My own husband was diagnosed with this same cancer 5 and a half years ago. He is alive and well. So take a deep breath and have lots of hope. Be positive in your thinking. Yes, this will be a difficult 6 months or so for you , but you will both get through this. How lucky is your Dad to have you. You will be a tower of positive support for him through this, I know.
Christine will be along shortly to give you further advice on general items and nutrition. Her advice is the best so I will leave it here.
Come here often for support, advice or to vent. We will all help as best we can. This site by the way , is the best you could have found .
Please keep us updated and have hope.
Tammy

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!