Yes, you can leave the pins floating if you do not use it.
It is not necessary to provide 22 ohms on the UART/SPI lines. WE recommend using 22-Ω series termination resistors to avoid reflection on GPIF lines
Please refer the app note for more: http://www.cypress.com/file/139936/download
My FX3 lanes run ~0.7" long straight in to the FPGA. Do you still see a need for the 22 ohm resistors? Not a big deal adding them but adds work. Thank!