So you still think that 3BB is the issue?
Your internet provider has no influence on your operating system of your PC.
The ISP delivers the speed to the modem/router, and everything that happens past the router, they can't control.
It is a simple test to take your AIO to your son's room and connect it there, but you will get the same speeds.
My money is on the low spec of your PC. AIO PC's are not really known for their high specs, but most have low processing power and RAM, maybe an Intel I3, and poor Ethernet adapters.
If you don't have the 25 digit code, then I also think you have a copy Windows, because all genuine Acer PC's with OEM windows, will have that code included or on a sticker on the bottom plate, and will have a recovery method to reinstall the OS from factory.