Why did the Nazgul not succeed in Bree and on Weathertop?

Whenever reading through Book 1 of LOtR, I have the impression that the lucky outcome of these events seems unrealistic, even in the context of a fairy-tale like story. In my opinion, there are at least three points where the Nazgul really must have got the Ring:

First, the "Prancing Pony" in Bree: After Frodo's disappearance, they know that the Ring is in front of them. The Hobbits are not able to withstand them at this point, and neither do the people of Bree. Aragorn, as strong and brave he is, cannot do much either, apparently he does not have any (useable) weapon
at this time. Why did the Nazgul not dare to fight in this situation? The "standard" answer might be that they are just ghosts, but they are able to cut the Hobbit's pillows, so they must have some physical power.

The situation is even more striking at Wheathertop, where the company is alone, and Frodo is already seriously wounded.

The third point is the "Last Bridge" over the Greyflood river. With some knowledge of the geography of Eriador, this place must appear as the weakest point on the way to Rivendell to anyone. The Hobbits almost certainly have to cross this bridge, being far away from any help. Why do the Nazgul do not await and attack the company there? In contrast, at Bruinen ford, where they try their final attack, they must expect some powerful help to their enemies from Rivendell.

To summarize all this, the behaviour of the Nazgul seems very inconsequent to me, and this is unbelievable, given the price that they could win or lose: If they got the Ring in Eriador, the dark powers would have won forever. On the other hand, with the arrival of the Ring in Rivendell the war is in some sense already lost for Sauron & Co. He did of course not think of Gandalf's strategy that in the end causes his complete defeat, but from this point on he has to expect that some mighty person would conquer him using the Ring, which would almost certainly mean the end of his realm.

So, why did the Nazgul did not fight to the very end in this situation? Is it possible that -- deep in their heart -- they were still a bit human and did not really want Sauron's victory?