Do you use the PANO modem? If so, the Pano App can actually break down which device is using how much data.
Hulu: 1.35 GB per hour to stream Hulu's catalogue in HD, 3.6 GB per hour to live stream, and 7.2 GB per hour for 4K content.
3 hours should only be 21.7gb of data at 4k, make sure however that you don't just turn off the tv, but that you end the hulu app and exit it properly.
Also, do you have security cameras? Blink/Ring? They can use an excessive amount of data if you have the resolution set to maximum, and you are saving the info to the cloud. I have BLINK, and do NOT have a subscription, I have the SYNC module with 256gb thumb drive and it can store an inordinate amount of data, so, no need for subscription eating my wallet, and all my videos are saved till I no longer want them, and delete them.
Other things to look for, turn off ONEDRIVE on ALL of your devices! Gaming systems can use a lot of data when playing online games. Games that are totally stored and played locally don't use nearly as much data.
If there is any more I can do to assist, let me know. I am a computer engineer with a specialty in analog and digital communications, and worked for Cox for over 16 years, 12 years of that in the Data Tier 2 department, so trust me, I KNOW data, and can definitely help you determine what's using it.