I have what Comcast calls High Speed Internet with Performance Internet Service. They gave me the "Performance" upgrade a year or two ago with no added charge and it made a BIG difference. I routinely get 15-20 MBps downloads since that happened. I pay $53.95 a month, which is about what it's been for years.

Your wireless router should have no adverse effect on the speeds we are talking about unless it is really old or not configured properly. I also have my own Motorola cable modem (which I upgraded a few years ago) so I don't pay the monthly rental fee for the Comcast-provided box (only $2 or so a month). I don't have fiber to the home, only the normal coax used for cable TV service.

I have IP phone service run off the Comcast internet, but I don't get the phone service from Comcast. I bought the telephone adaptor from Ooma several years ago at a one time cost of about $250. Since then I pay no monthly charge and no per-call charge, so the phone service is free. Since I don't use the phone at the same time I browse the web, I don't see any change in speed, but suspect it would be negligible if I did look for it.

I'm guessing they are throttling your data stream because you have the basic low speed service.

Comcast has been a very reliable provider with an interruption maybe once a year. The reason is never explained but has never been more than a few hours. A local construction contractor did inadvertently cut the coax a few blocks from my home about 10 years ago and that was out for a day or so, but can't blame Comcast. The contractor didn't "call before you dig" as they say in the phone bills.