I don't see Starter being a culprit in THIS scenario, although no doubt it IS cranking slow and this could be one additional cause but with the correct Firing Order, Ignition Timing, and proper Fuel Flow, it should catch it after a couple of rotations (in my opinion).
First simple way... Try a push start, if it starts, this will eliminate further discussion and we'd get to know that Starter is the culprit. Howver, IF not...
I doubt a few things here in your setup, I'm not dead sure as it is hard to tell from the video and photos but I see the Timing way too out, as well as Firing Order, again, to be sure we'd need to remove the Distributor Cap to check Top Dead Center on your motor.
Now it is possible to start the engine with the timing out but here it SEEMS way out and could be the cause of no spark at all. I'm sure your mechanic must've checked Points Gap, Coil, Rotor sitting properly on the shaft etc, sometimes such little things are overlooked even by the professionals and they end up in a headache.
Now for the firing order, I don't know why I doubt that Plug wires are connected 1-4-3-2 anticlockwise on Distributor. From the photos, they simply don't seem correct to me.
Next time you go to see the Blue, make sure you take AsadIshaque along, so he may check the orders and little details by himself as we always had our doubts on this mechanic but NOT on Asad ofcourse.