You could easily get two rows of four plus a bar in that room. It would be more difficult to frame, but you could go with a stair-stepped ceiling similar to some of the DE designs to make the best use of your ceiling height, but may not be worth it for 3". With a 8.5' - 9' ceiling, I would limit it to a single riser, hence a third row bar instead of a row of seats. You run out of space pretty quickly with a 9' ceiling (ask me how I know
Depending on how close you like to sit, your first row will end up at 1 to 1.5 times the screen width (generally speaking). This is very much a personal preference. If you like to sit further away, consider a second row prime seating. If you like to sit closer, maybe a first row works better. Once a row is decided on, you need to allow 7' of space for the other row.
Choosing equipment before the room is built can be a bad idea because you design the permanent structure around pieces that will change, though it does help with some decisions. Why did you choose in-wall speakers? With a room that large, there's really no reason to use in-walls unless you already have them, or are particularly fond of them.
Soundproofing the room is always advised here. You should probably get in touch with Ted at the soundproofing company and figure out your best approach. The most common approach I see here is to decouple from the framing using clips and channel, then add two layers of 5/8" drywall with Green Glue between. Since this room is inside a concrete shell, you may be able to skip the clips and channel and just frame a room inside the concrete shell that is completely decoupled from the house. That would probably be the cheaper option. For soundproofing, double doors are not a great idea either. Building a decoupled room inside a concrete shell sounds like a plan for great sound isolation.
You need to consider HVAC! My experience so far is that rooms this big tend to be easier to cool most of the time when it's just one or two people in there. My room stays cool with up to three people working in there with lights on and only the HVAC blower running (no cooling). However, I suspect that once you pack it full of people for a super bowl party, you may find that your HVAC is going to have to work harder. It is much easier to figure out how to get the air in and out now than it is to figure out once the framing is done. You're going to need much more air in that room than your typical HVAC designer is going to plan for.
If you're new to this, I would highly recommend you get in touch with Nyal at Acoustic Frontiers or SierraMikeBravo with Erskine Group and discuss options for a layout and acoustic analysis. Having a solid plan at the beginning will go a long way towards making a great space at the end. You are going to need acoustic treatments, and you might as well make sure you do it right. The cost of a layout and acoustic analysis is a drop in the bucket compared to what you're going to spend on building this room.