Faraday explains his time travel theory by saying think of it like a skipping record.

What if, Richard is trapped on the skipping record just like 'dan, charlotte, juliet, sawyer, and the rest" are trapped on a subsequent skipping record. We have seen Richard as far back as meeting Locke as a young boy, to recruiting Juliet, etc just lik we now are seeing Faraday back in the 50's at the Dharma initiative beginnings, up until the current day. Maybe Richard has been there for a long time, and understands how to travel 'forward or backwards on that street' since he can't change the street, whatever must have happened that caused the record to skip needs to somehow be reversed in order to get Richard back on track.... since Richard has been 'skipping' for so long maybe everyone who has been drawn to the island is the result of whatever caused that initial skip therefore they don't really exist.....