Lennox M/N G23Q3/4-100-6 Problem
Your frugal attitude towards annual furnace maintenance is what is causing your problem, That series of Lennox you own has had several updates on the ignition system that would have been covered by the factory if you'd had a Lennox dealer doing your annual maintenance.
BTW, your plan for a wood stove and liner is way more money than it would cost to correct your furnace problem.
Again as i have said....penny wise pound foolish.
Just slow, not stupid.