Temperature compensation of LSM303DLHC accelerometer / magnetometer
These are really questions you should be asking the manufacturer.  If the datasheet doesn't say anything beyond the maximum possible change due to temperature, then we can't answer this.

However, temperature dependence is usually a low frequency curve.  Common ways to do temperature compensation is by polynomial fit or lookup table.  Usually the lookup table approach is simpler in the firmware and will take less space and cycles unless you already have floating point routines loaded for some other reason.  Something like a 16 point table used with linear interpolation is probably plenty good enough.  This table would provide the offset value to add based on the current measured temperature.  Actually it doesn't need to be real temperature.  The table index can be based on the raw temperature sensor reading, regardless of how linear or calibrated that is.  In other words, the table says that when the temperature sensor says X, you add Y to the accelleration reading.  You don't need to care what the units of X are.

Yes, you will likely need to calibrate each unit individually in production.  That compesates both for the errors in the temperature sensor and the temperature dependence of the accellerometer.

1/2 g per degree, really!!?  That means that after only a 2&deg; change, you could be off by 1 g.  Unless this is meant to measure 100s of g, that's ridiculous.