I know quite a bit about FB so here's what I would do...
Use an image of someone grabbing their back, actually 3 images and maybe 1 cartoon image
Target people 30+ and your region, no other targeting needed as FB will optimize the campaign as you lose money at the beginning
***Give a reason to come: Free Analysis Worth $100, Get 1 Visit Get 1 Free, etc.. You need to test various angles, angles are everything. One angle might be "The 3 Deadly Issues With Back Pain" that you can use as clickbait (legit clickbait) and build up a retargeting list plus have a sign-up for help so you can build out the cheapest retargeting for Adroll + having the signup on the bottom of the page.
Run the campaign with 3 angles and 3-4 images
Make sure the lander does something specific like get their email and date as an appointment or Click To Call
Run Adroll all over the internet to get them back to the site with a conversion pixel to exclude them after they convert.