Adding a bathroom fan, how do I splice power into a switch that is 3-way?

First photo is the “main” switch and the second is the additional switch. Third and fourth are the combo switch I used in the past but I’m not sure if it will work for 3-way light switching.

Hey all, I’m finally getting around to adding in an exhaust fan in our upstairs bathroom. I got the fan installed, and ducted out the roof, and wire pulled down next to the switch. I’ve don’t a combo switch before with 14-3 coming from the light and 14-2 the fan. However, this light switch is a 3-way. On one side of the vanity is the “main” switch (has two black and one white wire going to the switch, one black is spliced to the other black wires in the box) and on the other is the additional switch (just red white and black wire)

My question is can I add another combo switch for the light and the fan into the “main” box, or do I need a separate switch for the fan and splice into the lights power, since the combo switch may not work for 3-way? Or do I need to tap the fan wiring elsewhere? I’m assuming the fan only needs to be 14-2, but I pulled 14-3 just in case.