Vaseline is the worst option, it will eat through the plastic and that's how you get a broken core.
Don't worry about learning a new method, keep going with what you know for the next week and understand that speed doesn't matter. As for learning the "whole darn F2L" I personally believe that...
If by "last part" you are referring to solving a 3x3 after having completed reduction method on a 4x4 and 5x5 to get centers and edges then either method works fine. The difficult part (at least for me) is working on finger tricks and doing algorithms despite my hands moving slower.
Is this where I go for pity?
I first learned how to solve a cube in '08 and while I wasn't actively speedsolving in all of that time, I was for a lot of the last 4 years and I'm still not sub-20.
But assuming that you might, for example, have an unlubed v-cube what might you suggest to lube/sandpaper it?
I'm willing to search for methods on my own, but what is the most popular/best decision?
Don't be scared if your times go up Bh13. Lube makes the cube faster, but your hands take time to adjust as well. Overall it will be worth it however. You should be able to shave off a lot more than a few seconds after a week of practice.
Maybe you should take a break. I have done some 300-solves-a-day weeks but I wouldn't get any faster. Leave and come back in a few days and your hands might be better. Also, too much cubing can hurts your wrists.
On another note: Solve big cubes and 3x3 will look a lot easier.
You should solve it on the bottom because that eliminates a x2 (rotation to get yellow on the top). As for help... did you even bother to read this thread? Post 1 has a lot of links to tutorials.