Just a few comments. A toxic smell is a result of a leak. The burning of ethylene glycol (antifreeze) is the culprit. Just after a leak occurrence in the copper tube, you'll hear noises. Bangs, pops and snaps. It's done. Turn it off at the breaker and have a professional remove or replace. The original thermostat has mercury. BE VERY CAREFUL. Have a professional fix or replace. One last thing. An electric bill as high as $500, what normally was $350, can be the result of adding just one oil draped space heating with maximum power of 1500 watts.
