I cannot tell you if that is exactly right as i dont know who the influencer is.
But i can tell you unfortunately your calculations / campaign expectations are wrong and you wont hit anywhere near your target.
If engagement is lets say 4% of 17,000 that is 680 and you will be hitting 6% of that, so about 40, not the whole 17,000 as engagement is not 100%.
But it is also the wrong campaign model, so i dont think you will even hit that.
You are best building an opt-in landing page for a free guide and driving the traffic to that. Then they become your list and you run an email upsell campaign.
Or simply set up your own ig page and get them to follow you on there.
But selling direct wont work so well for this.