there's the word Battle in the battle of the Atlantic, 783 of 1183 total submarines and most of the german surface fleet were destroyed in this same period. they weren't sitting on their asses letting germans plink their shipping, anti-submarine warfare technology was continually improving and letting the allies destroy german naval assets. there's a kernel of plausibility in a blockade being accomplished with submarines, like Japan was by the US, but the germans are missing the essential ingredient to that: the destruction of the enemy fleet so it can't retaliate and protect it's shipping. even so, how long did Japan keep up the fight under a total blockade? 2-3 years? i'd like to see the state of the mighty third reich in 1946 after 6 years of blockade, resistance, and cannibalization of industry

there's little to suggest they were eager to invade occupied German territory

just the universal view that war was inevitable, an ideological commitment to anti-fascism, and an unavoidable humanitarian impetus once the nazis start mass-killings? but they need not even advance, once the army is ready there'd be no reason to supply the germans further, precipitating their attack or collapse from lack of resources.

lower standard of living at the end of the war than at the start

nobody disputes this, but you're refusing to compare them to anybody else, people were dying of starvation in the rest of the world, in victorious nations like the USSR even. the germans were dying in the hundreds of thousands at the end of the war.

exactly how is british people being a bit malnutritioned compared to germany's literal plan to starve millions of people because germany could not feed itself under blockade a point for germany being able to starve out the UK? your conclusion is a perfect opposite of the what these facts suggest.