You might first look to the problem of one equation,
two unknowns - Iin and efficiency, one must have a
value assigned, but each depends on the other.
Then there's the treatment of the input current and
voltage waveforms and the output I, V. I recommend
(if in Cadence) using Calculator avg(clip((i(vin)*v(VIN)),t1, t2)
to get an average power for a time-range where things
are (periodic) steady-state, excluding the ramp interval
and capacitor charging currents etc. Same for Vout, then
get an efficiency and then compare results to lightweight
theory.