I'm having trouble with a circuit that needs about .7mA, the voltage in the port falls to 150 mV when I write a one to it.
This is very confusing, you talk about sinking current, in which case 150mV is fantastic, then you say writing a '1' to it which should make it stop sinking.
Anyhow, the amount of current the ports can sink or source varies greatly from derivative to derivative.
A rule of (my) thumb is that if ANYTHING but logic inputs is to be driven use a buffer.

Erik