+1 to what Shivanshu said. It is best to keep the tyre pressure at normal recommended levels.
Of course, if you’re planning to do off-road driving in slush, snow or sand, then it is best to reduce tyre pressure and that too only if you can top it up after that section is over. Otherwise your tyre will run a greater chance of getting punctured.
As for TPMS, they are available. However, most of them are from Chinese brands.