D-Day likewise has nothing to do with him declaring war on the USA. All that did was make it official, he knew they would declare war on him since they were already attacking him via lend-lease and because they just declared war on Japan, another Axis country.
>3) Hitler knew a two-front war was something he had to avoid at all costs. He told many times that it was that which had lead to the defeat during WWI. But what does he do ? He attacks USSR before having destroyed England, thus creating a... two-front war.
Again, this man knows absolutely nothing about the actual military history of WWII. The British threat was practically neutralised before Barbarossa. They were stranded on an island, and lost in North Africa and Greece, only having any success in Iraq. The war between Germany and the USSR for the duration of 1941 was practically a one-front war.