3 way switch wiring for heater
This is a job for a programmable thermostat, not a timer switch

The heater in question, a Cadet RM162, is a 240VAC unit, hence the two pole switch (which was inadvertently disassembled by the OP).  The timer switch the OP has, unfortunately, is a single pole, 120VAC unit.  While a relay could be used to get around this limitation, it's cheaper and easier to use a line-voltage programmable thermostat instead, such as the Honeywell TL8230A1003.