In the flashback to Locke's lunch hour at the box company, he names Norman Croucher as having climbed Mount Everest despite being a double amputee. Croucher was a double amputee, but the mountain he climbed was Cho Oyu (still the world's sixth-tallest) and not Everest.
Helen is first introduced as a friend John met while making phone calls to a paid telephone companion service. He claims to have been speaking to her for 8 months when he asks her to go to Australia with him. Later in the series, John meets Helen at a group therapy session.
Locke speaks on the phone to a woman named Helen, whom he offers to take to his walkabout, but she can't get involved with her clients. She also mentions that they had been speaking for only a few months. Later in the series, we find that Locke was romantically attached to a woman named Helen to whom he proposed. This is an attempt by Locke to re-create his relationship with Helen, who rejected his proposal and left him.
When Claire gives Sayid the envelope, she says it has his name on it. While she might have deduced it was Sayid's since it's in Arabic, unless Claire actually is able to read Arabic, she wouldn't know his name was on it.