Bricks in cargo area
A few years ago I loaded granite river bed rock into my 95 Jeep GC with the seats down and plywood on the floor. Granite weighs 250 pcf, nearly twice what concrete weighs. I thought I could fill the back up to a foot high until I saw the suspension giving way and the back end dropping considerably with one layer of rocks. It didn't take much to overload it and I was worried about breaking an axle. I made many trips to the wash to collect rocks for our dry landscape. A small gravel trailer would have been better.
The Toyota T4R has a rated cargo capacity. Look in the specs on the Toyota website for it. Even then, I wouldn't stack bricks over the back seats. Take the seats out, lay down a tarp and then cover it with wood blocks to level it and boards on top of the blocks to get a flat surface. Put board runners in front and along the sides to protect the front seats and all that interior body plastic. Make 2 or 3 trips with it. By the time you do all that you could go rent a small trailer.
Estimate the total weight by weighing a sample of known volume. Multiply that by the number of samples in the total volume. Red bricks weigh less than concrete.