It's possible the impression share loss due to rank includes losing out on impressions that the campaign is eligible for but are very broad so you would not want to show for them anyway.
You will receive a full report each month on your campaigns’ performance.
A good remarketing strategy...
Wait a month or two (because you need to have good enough performance from one platform before testing new networks because it’s always an investment to start a new network and therefore a new learning period) and then launch a Facebook remarketing campaign.