Paul_KD7HB:
You are absolutely correct. But we are discussing using the USB connection to a PC. This is NOT the normal serial data connection. Look up USB specifications.
Possibly, but the OP talks about an Uno and an Uno uses a UART to communicated with the serial-to-usb chip. So all communication is limited by the UART in the 328P.
If OP needs faster, higher baudrates are the way to go. Or switch to an Arduino with native USB support; in that case, keep in mind that disconnecting the Arduino from the PC (while externally powered) will eventually bring the Arduino to a grinding halt if you do not take precautions.