You'll be fine with that setup. Barbs and tubing will all fit together fine. You may need some hose clips/cable ties to create a properly tight seal, but not used 3/8" tubing for a while so cant remember sorry. To create a properly tight seal without these I'd say use 1/2" barbs and 7/16" tubing. Creates a very tight seal, but the tubing cant be bent as tightly as 3/8".
As for fluid, you'll probably only need 1 bottle. My current loop uses about 750ml (EK 150 res, GPU, CPU, TFC 120 rad, RS240 rad) so you'll probably use less than that.
As said, pump and rad arent the best but will be fine for your loop, just dont be expecting to go adding in many more blocks, if you do the pump will struggle to push the fluid round and the rad will struggle to get rid of heat fast enough lol.
That rad isnt too bad though, got one in my loop along with a single TFC. Used to have just the RS240 and it cooled an E8400 @ 4.4GHz and my NB very well, never over 70C using IBT. Its a fine rad for a simple loop
Good look with your build too, feel free to ask any more questions on here
