Right. The thing to keep in mind is that the U.S. was already doing full-scale materiel support for the Allies. No matter how much alternate-history Hitler might have wanted to play nice with America to keep us out of the war, he had a U-boat fleet and he needed to use it to stop the endless flow of ships to Britain. That was always bound to lead to war sooner or later.
Yup. In my opinion the US war against Germany was an absolutely necessary war. The sooner in the better. Longer to get in the more of Eastern Europe Stalin would have taken and never let go of when all was said and done - absence an insane attempt to to war with the USSR.
If a majority of the US Congress had been of your opinion, then the US would have declared war on Germany long before Pearl Harbor (and indeed, the attack on Pearl would have likely been impossible for Japan to bring off, if the US had been on a war footing at the time).
The same reasons for not declaring war against Germany in September 1939, when the UK and France did (Or in May 1940, when the Germans invaded France and the Low Countries; Or in June 1940 when the Germans completed their conquest of the Western European mainland; Or at any time between September 1940 and May 1941 when the Germans were bombing British cities) still prevailed in December 1941, right up until Hitler rendered the question moot by his declaration against the USA.
Pearl Harbor didn't significantly change the situation in the Atlantic or European theatres as far as the USA was concerned, and there were plenty of good arguments for Americans avoiding a two front (or two ocean) war by maintaining neutrality towards the Germans.
Nobody prior to the Battle of Stalingrad in the winter of 1942-3 was seriously considering the possibility of a Soviet re-invasion and re-annexation of Eastern Europe, after their having been pushed out of Poland by the Germans. The question up to that point was whether the USSR could survive, not whether she could defeat Hitler's forces so comprehensively as to push them back outside the borders of the pre-war Soviet Union.
Again, if Soviet dominance over Eastern European territories was a concern for Congress, they could and should have declared war on the USSR and/or Germany in 1939, when those nations invaded Poland. Of course, at that time they were happy enough with Hitler keeping Stalin in check. The concern about a post-war Soviet dominated bloc in Eastern Europe that you are raising would have been anachronistic in 1942 or earlier, and couldn't have been a factor in the decisions of US Congressmen, unless they had a time machine or a psychic ability to predict the Cold War. It doubtless played a part in strategic and diplomatic considerations as the Soviets rallied in 1943-4, but by then the question of US neutrality with respect to Germany was long since resolved.