First, it's not GIG, it's Megabytes per second.
Second, 4K tv requires between 15 - 50 mbps, depending on the level of compression, HD requires 5mbps, so unless you are uploading uncompressed 4k, 35 mbps is more than enough for streaming up.
Third, your wifi vacs and bulbs do not use internet normally, they use internal LAN connectivity, and your WAN speed has no affect on them, and your security cameras, unless they are recording to an external to your home dvr, they also would be on the LAN. If they record to a third party DVR however, they could be using a LOT of bandwidth.
MY Internet is 500 down/50 up, 
I stream up and down with ZERO issues. In fact the other night I was streaming to my daughter's 4k tv a wuxia tv series I have, while I was watching "The Blacklist" on Netflix at 4K.
lastly, I SERIOUSLY doubt you called tech and found them closed after hours, because Cox Tech Support is 24x7 every day of the year, including ALL holidays. I know, because I worked there for 1 year in Data/Telephone/cable Tier 1, 11 years in Data Tier 2, and 4 years in CAG.
BTW, I have BOTH Internet and home phone service for 79$ a month, and again my 500 down/50 up is far more than enough to do everything I need, and then some, and as a 100% disabled veteran, I TOO am concerned about cost of services. BTW, You can get Verizon plus, unlimited talk/text/data for 45$ a month and for 10$ more, get Netflix and Max. Not sure what T-mobile provides, but I can tell you that 45$ unlimited and then 10$ for netflix and max is a heckuva deal. Again, I know this because I am concerned about $ in and $ out. Since I can no longer work, it's important I reign in all my costs.
If you are using a compression card, something like an Elgato 4K pro, and a good video card, Nvidia 4070, you should be able to handle a 4K capture and stream using about 27mbps, and still have bandwidth left over for your security cameras. If you need assistance with setup, you can check back with me, I do system design, and have been doing it for over 40 years.
