I just looked at your photo. That really is a pronounced difference between the left and right sit bones depressions. What about a new non-leather saddle that doesn't stretch? That way you would be sitting more level and it might make a favorable change in your biomechanics. Just a thought.
Also saddlesores comments about weight and gearing seem like they could really help if applicable. Maybe a few tweaks (rest, saddle change, weight/gearing changes) will cumulatively make a difference.