If the valve is solenoid activated, that is has wires controlling it, then all you need to do is open that valve and the ice maker line will back drain. You do need to then let the ice maker run through a cycle to make certain it dumps any ice in process. If it is just a check valve you need to hold it open while the ice maker runs through a cycle to allow the water to back drain when the solenoid valve opens.
I would not let pink stuff into the ice maker because on the boat we had before getting back to a land-based RV the ice maker specifically said the pink RV antifreeze would ruin the plastic. Not sure if this applies.
Re the filter, I remove the cartridge, let the filter tank fill as I winterize, then take the tank off and use what is in it to dump into the drains to fill the traps. When de-winterizing I run enough water into the filter to clear any antifreeze in the line from the pump, then dump it, install the filter cartridge, then run the water as normal to flush the rest of the lines.
Dave