Unfortunately, there's no way to determine the actual cause of the slow down.
For instance, you said that the slow down happens after 5pm, which quite literally is when 80+% of the working force gets off work. It could also be an artifact of AWS, and not Verizon FIOS.
Also, 2 instances does not a trend make. There's no way to know if you're one of those people who were sent a letter because they were using terabytes of data a month, and they're simply protecting the network traffic of 99% of their other users. Granted, I assume you aren't, but I can't be 100% sure.
For a truly independent test, you'd need the same modem/access device, without a local switch (i.e. a machine connected directly to the modem), and you would need VPN access to test both identifiable and non-identifiable traffic.
If you could verify that Netflix traffic through the VPN, on the same network, without any interference through the router, was delivering much more bandwidth than the same Netflix traffic, but in the open (not through the VPN), and could do so for a statistically significant portion of the Verizon FIOS user base, then you'd have reason to complain. Until then, I don't see your claim being taken very seriously.
Just my opinion though, ymmv
Is networking the most frustratingly complex field in technology? As someone who admittedly knows little about it it all seems like a pile of hacks stacked on top of one another. It's the only explanation I can come up for why it's near impossible to figure out why a network isn't behaving correctly.