You'd probably make it to the old lookout hut on your first day, but don't count on finding much water there, fill up before you start the ascent from the jeep track. Be warned that you may have lots of smugglers passing through your campsite at night, and be very careful of hiking around there at sunset - this is often when smugglers are coming down and where they get ambushed by the authorities. Hikers have been shot at during the night in this area because the smugglers thought they were being attacked.
The smuggling route, or "Smugglers Pass" as I call it (because it has its own, distinct summit and is not the same as Thuthumi Pass), it a very viable route for linking Thuthumi Pass with Organ Pipes. The link is not too far down Thuthumi Pass, and it would be a much quicker route back to Mikes Pass than walking out Thuthumi.
Enjoy, but please consider the risks of this area and be careful!