Need DEQ wiring layout and parts help... Wireless Line Array (First Build)

I usually design furniture but I've always had an interest in Audio Equipment, so i thought I'd finally take the plunge and build my own speakers. The original idea was to build a Line Array that I could connect my phone or laptop to wirelessly… I got in a bit over my head.

I've included diagrams of how I am setting up the system with a toslink connection before the deq. (Originally I planned on analogue in to the DEQ but things got a bit complicated and I don't have that much room to work with in the enclosure I am designing. I'm including it here as a reference to my fallback design if using an optical in is fundamentally flawed.)


Analogue Alternative Backup Version

Question 1: How can i add a master control to the volume? I've been looking at the DIY LPA and the CL-RLC, but I'm unsure of where to hook them up at in the system. I figured it would go okay between the DEQ and the amp board, but I don't know if they would cause clipping or distortion.
DIY Lightspeed Passive Attenuator

Question 2: what am i missing from my setup? This is a serious question, i'm unsure if there are discrepancies between the input and output levels of each of the components. Do i need Passive Attenuators or anything anywhere in my setup? (I'm not totally sure of what a Passive Attenuator is or how to use one)

Question 3: are there any fundamental flaws? Am I over simplifying or over complicating the design?

Question 4: Is there a way for me to split the toslink in to select between two audio sources easily? This isn't necessary, but would be a nice extra.

Here is the Parts List:

Dayton Audio ND90 8ohm (x48) 24 per channel
Dayton Audio ND90-8 3-1/2" Aluminum Cone Full-Range Driver 8 290-210

Speaker Wire:
16 Gague

Material: Walnut or hard maple
Volume: 1.5l Sealed

Amplifier Board:
Sure/Parts Express
2x300W TAS5630 Class-D Amplifier Board
2x300W TAS5630 Class-D Amplifier Board 320-309

Amplifier Power Supply:
48 VDC 12.5A 600W Regulated Power Supply
48 VDC 12.5A 600W Regulated Power Supply 320-317

DEQ - Behringer DEQ2496 Ultracurve Pro
Digital EQ/RTA
Behringer DEQ2496 Ultracurve Pro Digital EQ/RTA 248-661

Airport express
Toslink out

Behringer ECM8000

Any help would be appreciated, thanks.