these orchard-tufts, Which at this season, with their unripe fruits, Are clad in one green hue, and lose themselves 'Mid groves and copses. (11-14)
The "unripe fruits" of Line 12 will, eventually, and in Nature's good time, transform into ripe fruit. Perhaps they're supposed to represent the kind of mind that the speaker used to possess, the kind of mind that could appreciate nature, but couldn't "see into the life of things" (49).
I have […] felt in the blood, and felt along the heart; And passing even into my purer mind, With tranquil restoration: (26-30)
The memory of the "beauteous forms" (22) actually causes a physical change in the speaker. He feels it "in the blood" and "along the heart." It's the healing power of nature.
While here I stand, not only with the sense Of present pleasure, but with the pleasing thoughts That in this moment there is life and food For future years. (62-65)
As the speaker is standing on the banks of the Wye, soaking up the beauty he sees there, he imagines that in "future years" he'll be able to turn to these memories with "pleasure." He imagines that he'll continue to change and evolve as a result of his relationship with Nature.
And so I dare to hope, Though changed, no doubt, from what I was when first I came among these hills; (65-67)
The speaker recognizes that he has "changed" since his first visit, although he might not have recognized the transformation as it was taking place.
— I cannot paint What then I was (75-76)
The speaker is now so far removed from his past self that he has trouble describing it. Or perhaps he just has trouble putting it into words.
That time is past, And all its aching joys are now no more, And all its dizzy raptures. Not for this Faint I, nor mourn nor murmur; other gifts Have followed; (83-87)
The speaker realizes that his innocent, unreflecting enjoyment of Nature is over. He has become conscious of the "presence" in nature, and he can't go back to the way he was.