Pullup resistor value based on current sinking capabilities
Yes, that is only applicable if your have an external signal driving the OE. Simplest is to just tie the pin to VCC.Good practice is also not to let any unused inputs float. Tie all inputs off high or low. I would use what ever is simplest in the PCB layout. 


  Am I right in thinking it's just using Ohm's law, which would give a resistor value of 330Ω 


You don't need a resistor but if you do, you want the pull-up as light as possible to avoid unnecessary power consumption and high speed. The lower the pull-up resistor the higher the current and the slower the port will switch. Go for something like 10K.

Is there a reason why you are not using dedicated level converter? Also in many cases just a resistor divider will suffice.