Your #3 was really a big one. Hitler probably could have recruited large allied armies from Ukraine, Belarus, and the Baltic States if he had just allowed himself to treat their populations as something other than subhumans. The failure of Hitler’s invasion was no sure thing; a large allied army fighting against the Soviets instead of harassing the Germans and forcing many German soldiers into garrison duty behind the front lines might well have turned the tide.
I wouild also add failing to bypass Stalingrad to your list. Taking the city itself, even without the subsequent siege and loss of the 6th army, actually gained no strategic value for the Germans. The strategic goal was to interdict river traffic on the Volga, a goal that could be accomplished without actual control of Stalingrad. Hitler insisted on taking the city primarily for propaganda purposes based on the fact that it was named for Stalin. Bypassing the city, leaving a garrison on the river to control traffic and pushing toward the Caucus oil fields would have been a far better use of Hitler’s troops.
I can see the strategic value of Stalingrad as it was the biggest port and industrial city on the Volga.
Stalin seemed every bit as determined to defend the city as Hitler was determined to take the city and that’s what lead to the biggest and bloodiest battle in recorded human history.
The most perplexing aspect of the battle was Hitler’s stubborn refusal to authorize a breakout from the pocket while the 6th Army was still viable. ALL of his generals advised a breakout. Only RM Goering, perhaps his judgment impaired by his addiction to morphine, suggested the 6th Army could be supplied by an airlift-—pure insanity given the atrocious weather conditions. And Hitler himself by now given a daily injection of a cocktail of drugs supplied by his quack physician. Hitler’s lack of military logic probably is the reason he never rose higher than corporal when he served in the army.