How can I measure total current used
There are three ways to handle this.

1) ... buying one of those USB multimeters which can do this and splicing the wires to connect it in series with your circuit 

2) Measure the current manually with the magnet on, and again with the magnet off. Use a logger that records the time the magnet spends on. Then get the average current consumption over the period by computing the time weighted average of these two figures.

3) Use a logger that measures the current moment by moment. Read sufficiently often that the timing errors are small enough for your purposes. Integrate the readings to total charge, and then divide charge by total time to get average current.

What sort of logger? You can spend various amounts of money on standalone loggers with all sorts of fun inputs. My preference is to use an Arduino and read it from a program running on a PC. If you already use arduino, then that's a cinch. As you will probably need signal conditioning to get your current measurement into a voltage, it's a neat trick to use both high and low sensitivity amplifiers into two ADC channels, one optimised for the magnet current range, one for the controller range, and figure out which one to read at the time.