You are right though, it is true that a "stronger" solvent will dissolve DMT better if the pH isn`t so high.
A few things about that tek though: First of all, to make sodium carbonate from bicarbonate, I am not sure if 30 minutes in the oven will be enough, I`d leave for at least an hour, or make sure to weigh it before and after to make sure it lost about a third of its weight (or have a pH meter to be sure a solution with it is 11+), otherwise an incomplete conversion will mean too much sodium bicarbonate left which won`t raise your pH enough. Oh and, it`s 200c, not farenheit.
The otehr thing, you HAVE to use at least some water when mixing the base with the plant material, otherwise if they are dry you will not have the freebasing happening properly.
If you can find calcium hydroxide, that`d be an even better base than sodium carbonate if you do a dry tek
Another problem with this tek is that when you evaporate your vinegar, you will have the dmt in salt form (DMT acetate in this case due to acetic acid in vinegar), not DMT freebase, and while it may sort of work to smoke, it is definitely not recommended. Smoking salts instead of freebase might be more irritating to the throats and lungs or even possibly toxic, you should always smoke the freebase and use salts for ingesting. So you would have to convert it to freebase. Look up BLAB tek in the wiki for the `salting` step so you see how to do it with vinegar or fumaric acid (better IMO).
In fact, I recommend you to look into teks in the Nexus (check the FAQ and the wiki extraction teks section), since they have generally been double-checked and are more reliable.
Hope that helps