That is hard and you could cut the sweetcorn off to cook in water to make polenta.
Yes you simply left it too long.
Don’t grow it, there will have been cross pollination with any corn many km away including the farmers’ hybrids.
1 cob/plant is ok.
Farmers grow it close but their rows are perhaps wider apart, and they add a lot of fertiliser for 1 cob per plant.
