Hey Andreas, I may be wrong but I believe freeze 12 has a flamable chemical in it and therefore is not suitable for automotive use. As far as I know, there are no truly "legal" drop in replacements for r12 (I hope someone tells me I'm wrong here)I really don't have a clue about the POA valve, so I am no help on that question.
Really, I just wanted to put my 2 cents in and let everyone know to read the labels carefully on any refridgerant you buy. If is dosen't say for autonotive use, it has something flamable in it and can be very dangerous.
Jim