Unless you can absolutely guarantee no traffic jams, you'd ideally need to leave before the end of the race to get to Le Havre for 19.00. The timing of that crossing is a nuisance!
Personally I'd take the motorway up to Alencon North, get off there, then up the N138 to Gace, then D579 up to Vimoutiers, Lisieux, then Pont Leveque onto the E46/A29 to Le Havre. It's a scenic route, fast roads, never any traffic, never any speed traps once you're past Gace and this might help make up for missing your extra day in France.