An He 111 should have had a radius of about 750km (450miles?) With a 4400lb bomb load and one hour reserve.
Not quite as good as the Wellington but not too shabby for a "tactical" bomber.
What are the operational figures for a 1940 He 111?
The luftwaffe was not developed with the foresight that encompassed long range massed bombing formations. Blitzkreig was the order of the day, achieved with Ju 87's for close support,
The battle of Britain showed up some obvious flaws in the strategic level, as well as proving the vulnerability of the JU 87 without adequate escort.
Like so many of the major mistakes made ( like invading Poland in the first place),the Luftwaffe could never had delivered what was required of it.
Using two coupled engines to drive one prop was a mechanical absurdity, leading to extensive maintainence and cooling issues.
Even Goering is quoted as stating that asking a 4 engine bomber to dive was " complete lunacy".