Hopefully the missing power and ground connections in your schematic are actually there. You can probably get away with only using one ground connection to the RFM since it is a PCB, but you absolutely must connect all of the power and ground pins on the ATmega, in particular leaving out the analog one causes odd behavior in non-intuitive ways.
Also you are hopefully shutting down the ADC and its reference after use.
Be vary wary of signals asserted against pulling resistors.
Communication lines (serial etc) can either donate or steal current, a node may very well run off power stolen from a debug serial port or in circuit programmer up until it tries to transmit or receive at which point it will brown out. In other configurations such a connection may steal power.
Also never drive an I/O to a powered off component, it is generally out of spec and even if it does not cause damage it will be a power drain.
You may want to leave this thing running for hours on something that profiles what it actually uses. An INA219 hanging off another Arduino might work if you increase the sense resistor and bypass it with a capacitor - it may not accurately read the actual sleep current, but with some work on the current monitor Arduino sketch and running its output into a serial log program on a PC, you should be able to at least get a good idea of when it was awake and for how long, and to see the transmit and receive operations. I have mine rigged to start integrating any time power rises above the sleep baseline and then print out a total of microamp seconds when it goes back to sleep - I then merge the monitor output with the node debug output and I get logs to the effect of:
“RX1 at frequency…”
“no packet received” followed by an injected
“Current: that cost xxxxx microamp seconds”
Part of the goal there is to make sure software doesn’t get into a state where it is being far more active than it is supposed to. A watchdog can be useful, too - even if you have to wake up every now and then just to service it.
To measure the sleep current, rig the node to wake up do a transmit/receive cycle then go permanently back to sleep. You won’t get enough power through your meter on its most sensitive scale to run the node, so rig a clip lead across your meter leads and power up the node with that in series. After it’s done transmitting, remove the clip lead and see what you actually measure while sleeping.