While the words loneliness and solitude are both used to describe being alone, they don't quite mean the same thing. Solitude usually implies being a-okay with being alone. But loneliness? Not so much. We use solitude here because the speaker seems to really think that being alone would be the most peaceful, wonderful thing in the world.
Line 1: This is the speaker's first announcement that he's headed out of civilization to be alone in the country.
Line 2: The speaker wants to live in a modest cabin. That doesn't leave a ton of room for entertaining.
Line 4: This is the official declaration that the speaker wants to live totally alone. Without people, that is. He does seems pretty psyched about having nature's creatures for company.
Line 5: After getting away from it all, the speaker says he'll finally have some peace and quiet.
Line 9: The second time this line comes around, it really emphasizes the speaker's determination to get away.
Line 12: The speaker's connection with this place is so strong that it almost seems spiritual or romantic. No wonder he wants to be alone with it.