Measuring Current into a Boost Regulator

[wholder]

I'm designing a battery powered device that runs on 2 AAA cells boosted to 5 volts using a SEMTECH SC120, Low Voltage Synchronous Boost Regulator https://www.semtech.com/uploads/documents/sc120.pdf that, in turn, powers an ATTiny84A and some other circuitry.  I want to measure the current draw from the batteries under different load conditions, so I connected my multimeter in series with the battery input, as that seemed like it should work.  Wrong...  Instead, I get all kinds of weird symptoms ranging from the multimeter sometimes showing a large current draw of 300 mA, vs my expectations of a draw under 30 mA.  The ATTiny84A seems to start up, as I see an LED  set in the init() code blink once, but then it seems to crash (I have a heartbeat LED that should be flashing if it's running.)

I tried adding various additional caps (.1 + 1uF + 100uF + 220uF, etc. in parallel) to the input terminals just before the boost reg input, but I still can't get to the point where the heartbeat LED will flash.  I also tried the different current ranges on the meter,  but the ATTiny84 flashes the heartbeat LED when I remove the meter from the circuit.  BTW, the multimeter is an EXTECH EX330 that I've had for many years.  So, what am I doing wrong?  Do I need a fancy, desktop multimeter, or is my approach flawed?  Any suggestions welcome.

Wayne