I'd suggest different tank dimensions. Although the dimensions you list would be great for a freshwater planted tank with all that height, it doesn't work well for reef tanks. Not only does it take a lot more lighting to get down to that depth, but it makes placing of rockwork really awkward. When you place your rocks in the tank they should not touch any of the walls of the tank to encourage better flow in the tank. For this reason I'd suggest the 40-gallon breeder tank which is 36 x 18 x 16".
If you get the 40 breeder it would fit that 36" T5 fixture that you have. Is this a 2-bulb fixture? If you really want LEDs (I'm not a fan), then you could add a blue strip to each side of the T5s and use the LEDs as supplemental lighting. For bulbs, I'd suggest blue bulbs in the 18,000-20,000K range, no white bulbs and no actinic bulbs. The blues work really well for soft corals and lower demand hard corals even. If you get the blue LED strips though, you may want to pick one white bulb in the 12-15,000K range.
If you're not going to get a skimmer, just use an AquaClear. Don't use any "biological" media in a saltwater tank. Just put filter pads (you can buy bulk rolls and cut to size) and carbon in it. You'll need to throw out the filter pads each week and put new ones in, don't rinse them. That's why I suggest the bulk ones rather than sponges - much cheaper!
Also, you probably only need 30 lbs of rock total, and for a 1" sand bed you'll need about 25 lbs of sand. Many of the bags come in 30 lb bags, so you could get one, but don't use it all. 0.5-1" sand bed is ideal unless you have a critter in there that
specifically needs a deeper sand bed. Most critters that
prefer deeper sand will be able to live in shallower sand just fine.
What types of fish and invertebrates do you plan to stock?