If you have the choice between getting invaded and selling iron to the enemy, I think the choice is quickly made.
Well. You can't leave Norway because the iron and some oil supply could be in danger, there are also the naval bases and the Allies might as well launch larger operations here. And Hitler believed so, in great shape because of his intelligence reports of "propable Allied invasion of Norway". He had already things that had happened there, many commando raids... He needed the materials and the aerial and naval bases. Although 400.000 men are TOO many... Maybe you could handle it with 50.000 and the other 350.000 would have been very useful elsewhere.
I believe one or more landing sites could have been neutralised but not all,I think an allied foothold was inevitable whatever defensive strategy was employed. The point made re air power is of most consequence in respect of movement of German armour,which was nigh on impossible during daylight hours and therefore SEVERELY restricted use of armour in an offensive capability (not shouting,just trying to seriously stress the point !).
Don't worry, Tommy - we shout at each other often here ( well, some of us do, anyway ! ).But webmaster Otto has provided a really useful 'italicize' or 'bold' option ( bottom left boxes when you're posting ) which I use a lot ! BTW, a very warm welcome to the Forums.....
Only if the Luftwaffe could have produced enough planes to gain a parity in the air to allow day time movement. Without air support the Germans will always lose.