Upload speed from 5.82 MPS to .44 MPS depending on time of day (100MPS plan)

I was seeing network issues while using Zoom, checked Speed Test and found upload running at less than 1MPS (I have a 100MPS plan; download was fine.)  I contacted Xfinity support about my poor upload speed.  They could not find anything wrong on remote diagnosis, so suggested a hardware check on the external cable connection box, followed if necessary by a possible paid check of my internal hardware.   Wanting to avoid both possible payment and contact, I checked different configurations on my internal setup and determined to my satisfaction that the problem was somewhere outwards starting with the cable into my house.

Later in the evening I happened to check Speed Test and...upload was 5.88 MPS.  So thought about it, and the next day, yesterday, I started logging upload speeds with screenshots, and carried that into the evening, and then picked it up again this morning.

The decrease in upload speed very closely correlates with the 8:30 AM to 5:30 PM working day.  I'm going to log that for a couple more days, however, I'm already pretty convinced that my upload speed issue is related to neighborhood traffic, i.e. everyone Zooming during working hours.

Question is, if I bring this to Comcast's attention, can and will they do anything about it?  I respect their problems with the unexpected upload volumes, however, I really need reliable fast uploads.  1) Do they have a contractual obligation to provide a minimum upload speed? 

2) Will vigorously complaining and promising escalation do any good? 

3) Will paying for faster download provide faster upload (even if crippled by traffic?)

Any guidance on this will be appreciated.

Thanks!