Hi, I did not want to hijack that thread. I retired recently, I was a splicer for Verizon. I placed, spliced, tested and turned up the fttp. The Actiontec routers are Mcoa (cable) ones, a lot of people cry and complain about them, but I think (IMO) they are excellent.
Yes, I used the speed optimizer, but I also have tried IOLO system mechanic to set my parameters for LAN, T1, and WAN(they all set TCP/IP, MTU, Black hole discovery, etc.) to different settings, which, you can do manually, if you want. I have seen not large changes to the download speeds. Like you my download speeds vary. The only speed which should be constant is between you and the C.O.(Central Office), after that it all depends on hops, ping times, usage, etc. Verizon speed test tests your connect between you and Verizon.