The first dream sounds like an elf experience of getting called to climb the white tower and look west in the palantir there.  The beginning of the dream of a high window in a dark forest does sound like a Gandalf connection. I believe at this point, Gandalf may already be captured and imprisoned at Orthanc. Or this part of the dream could be a growing sense of prescient foreboding that Frodo is feeling. In your re-wording of the dream, a key phrase was left out: "Then he knew that it was not leaves, but the sound of the Sea far-off; a sound he had never heard in waking life, though it had often troubled his dreams." (italics mine). Very curious... a hobbit who dreams of the sound of the sea and has been dreaming of that sound for a very long time. Pre or post ring? could be either. At this point, he has had the ring for 17 years. This dream gives me the impression that Frodo's spirit is "elvish" in tone. Possible UUT that Frodo is a reincarnated elf?

The second dream seems literally prescient to me. I think that had something to do with the effect of Tom Bombadil on Frodo.

In "Of Herbs and Stewed Rabbit" there is a quick reference to Frodo waking up to Sam's cooked coneys from "another gentle unrecoverable dream of peace." I'm pretty sure there are other dreams, but they are not indexed. I don't know where they are.

Very interesting topic. I will definitely be on the look out for his dreams while I (re) read LotR (just started again). In general, IIRC, Frodo seems to have different levels of dreams...sometimes they seem prescient, sometimes just jumbled reflections of what his life feels like and sometimes they bring awareness and comfort from a different plane.

"...men's hearts are not often as bad as their acts, and very seldom as bad as their words." Tolkien, letter #250.