Antifreeze smell from your heater is a classic sign of a leaking heater core (the heater core is essentially a little radiator that uses warm engine coolant to create warm air in the vehicle's cabin).
Heater core leaks often start very small, and might not be visible until the heater is disassembled.
This is likely unrelated to hard starting. Are other basic tune-up items for the van (spark plugs, wires, air filter, fuel filter, etc.) up to date?