3. Yes, it is possible to book one-way rewards on AF, KL and NW flights only for 50% of the rt miles
If you are elite with FB, you'll have access to one more reward inventory (economy only), not sure with OnePass. But, with FB you pay fuel surcharges on reward flights (even for partners' flights where partners do not charge fuel surcharge) and with OnePass you don't
FB customer service is notorious