This is where you need to start.
https://community.arubanetworks.com/t5/Validated-Reference-Design/Very-High-Density-802-11ac-Networks-Validated-Reference-Design/ta-p/230891
It likely has everything you need and anything over and above this would likely require a professional services engagement with one of our LPV partners.
Rough client per AP counts should be in the 75-100 clients per AP neighborhood, but the VRD goes in to this as well. Not knowing how many seats (maybe this is 10-15k seats?), you would need around 100-150 APs. But ballpark, for rough BOM'ing you shoudl scope 75 clients per AP, divide your seating capacity by 75 and round up to the nearest 10-25 (so if you have a 23,500 seat capacity, I would say 325 APs)
All APs firing inwards is a bad idea, that will 100% assure you that you will have to deal with a significant amount of ACI and CCI. Best cases are under seat AP deployments to allow the human bodies to help in attenuating the RF (creating small cells of RF), or APs above, down firing with narrow antennas, creating smaller cells of RF with a minimal amount of reflectivity. From your floor plan drawing, though, if those are the only APs you have, your WLAN will likely be over-loaded and perform very poorly.