Hello, I'm really sorry and saddened to read your post.
Unfortunately, your Drs are correct. The tumour can indeed erode through the Carotid artery. This will result in a catastrophic bleed out.
Blood doesn't look so frightening on dark material which is why they are advising you to get in a supply of dark towels. You will need towels to absorb the blood should the artery go.
I wish I could tell you more. Have you talked to Hospice about this eventuality?
If it was me, I would want to keep my Husband close to me, to spend his remaining time at home with his family. Have you a Parent, sister, close friend ,who could be at home with you to remove your Daughter should this scenario eventuate?
I know that there have been previous members here who have had to deal with this. look at the final,posts from "Kens Wife".
I will keep your family in my prayers.
Tammy