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your schematic is a part of PMOS transistor datasheet!
the table is [ABSOLUTE MAXIMUM RATING]
it say you must not allow that condition exceded. and you must use in far fram its parameter.
for example maximum drain source voltage is -30V , it means that you must not give voltage grater than , say (-25)-(-27) V.
the rest of them is obvious.
Another way to generate the -12V would be to use an inverting dc/dc converter -- this is sometimes known as a buck/boost converter. Do a google search and you will find lots of information about this converter. It is very popular and you can find control ICs from ON Semiconductor, National Semiconductor, Texas Instruments, etc.