2) The radar signature was not relevant, because German radars were anyway much less advanced and hardly used their radars to search for targets. Which German ships were top heavy? There were problems with sea-keeping in several ships, but for other reasons (e.g. in case of the destroyers).
4) I would be surprised if German is really easier to learn than English. Anyway, I would consider this point to be completely irrelevant. For spies the Allied had a much better source: Germans forced into exile by the Nazis.
11) The lead in armament the Germans had in 1939 would have been lost in 1942, when the British, French and US armament industry would have been fully developed. The German industry would have been probably collapsed, because of the severe debts and problems to get raw materials - one of the main reasons, why the war was started in 1939.
The much more obvious reason was not included: criminal idiots decided to attack countries, which combined had a much stronger economy and military.