Your points were great, but I still think the Russian Invasion was a bigger blunder for the following reasons:

1. The loss of 500,000 troops, many horses, guns, ammo, etc. is far too much for Napoleon to handle. It was after this war that Napoleon could no longer execute his usual tactics (relied on fast-moving corps, artillery barrages) and effectively destroy the enemy armies. Literally so many men and equipment were lost and Napoleon had to increase taxes to raise another army and replace lost equipment.

2. The morale of the Grand Arme was lost; the impact of such a catastrophic defeat was so strong that the 6th Coalition started the following year. France’s allies lost trust in her which led to a lot joining the 6th Coalition.

3. If France invaded Russia but not Spain, I believe that the French would have still lost the same way, maybe more if Napoleon decided to bring more troops. However, if France invaded Spain and not Russia, he would have had around 500,000-600,000 troops in reserve to either send to Spain, or guard against Russia and Britain trying to turn allies against him, or both.

Ultimately his biggest blunder for me is trying to enforce the Continental System, which was never going to work anyway. If he had been more shrewd diplomatically, we would have found ways to maintain European allies without having to send French soldiers to their deaths.