for having 3.3 volt without any load in P0, your pull up's must be higher than 3.3M
that is unsafe and also depending on the other end of the line which you do not show. The only way the size of 'R' affect the voltage is as a divider in combination with the leakage current of the output and input. Also at such low current, the voltage drop of the diodes will be a virtual zero(you are playing with half a microampere). Also, since this is leakage currents (both diodes and ports) it will be wildly temperature dependent.

In other words "unsafe at any speed".

Erik