I barely used half a tube on my oil pan, so you should be good with one tube. Assuming you get that Valco Cincinnati tube grip, which helped me tremendously.
1/2 a TUBE!?! I hope you have some tiny tube I don't know about... and the oil pan gasket is a Chinese invention and completely unnecessary. An oil pan gasket was used on the steel oil pans, like the AHU.
But the ALH and later models are cast Aluminum. Here's the thing about that oil pan. It's milled surface against milled surface. Almost ALL of the RTV is going to come out of the sealing surface, either inside or outside. The objective isn't to have some giant bead of silicone pushed out, or worse, dripping where you don't need it to go. When I'm done, there is a tiny line of sealant you can see on the outside. Before installing pan, be sure the screws and the pan has all of the old sealant removed.
I would guess that I don't use more than 10-12 pea-sized dots of RTV to do the entire oil pan seal. I spread it thin and make sure some gets into the bevel in the oil pan's bolt holes. I use the Reinz Black or the Dirko Orange. Either product works fine.
The other 'virtual crime' for oil pans is how much you tighten the bolt. It's 10 ft lbs. After you get the sealant right, truthfully it's the sealant that holds the bolts in. They aren't going to fall out.
From 'Hints, Tips and Tricks'...
The best way I've found to install the bolts when under the vehicle, is to use a 5mm long reach ball-end allen. The tool can be found with a 3/8" drive and a 6" reach. (Removal is best done with a 10mm 1/4" drive socket and a 1/4" drive 6" wobble extension). This is very handy when installing the screws that are hard to get to between the bell housing and the end of the oil pan. Even more so, with the manual transmission flywheels. Even to the point, there is a radial slot in the transmission side of the dual-mass flywheel that we align with the oil pan screws in the rear main seal to create easier access.
The cool thing about the ball allen is the oil pan screws will stick onto the end of that ball and even if held horizontally, won't fall off. You can reach up into the bell housing area and get exactly the right angle and hand-install those 4 screws.
Apply the sealant to the oil pan, then support the pan by installing 4 screws where they can be easily mounted around the perimeter LOOSELY. Using the ball allen tool, install the bell housing screws. Then, install the remaining total of 20 screws. Don't tighten any screw until all of them are installed.
I don't use a torque wrench. By holding the ratchet head, after the screw is seated, I use the 10mm socket and give each bolt a little nudge; maybe an 1/8 of a turn, at most. I do use Makita tools, like an impact driver, but lightly. If I hear it hit once or twice, the screw is tight.
More RTV and more torque DO NOT make a better job.