I don't know about the failure to report income, but I think there is much more to his admitting to lying.
Remember it was Strzok(high level deep state) he was speaking with, and even before Trump entering office a plan was made to take down the corrupt FBI and CIA- a large part of the deep state.
Flynn, a patriot, key player in the incoming administration and master of espionage likely designed much of the plan/traps.