Anita! You’re ahead of me! I’m so jealous. I’m going to catch up over the weekend. Gonna be a very blue weekend!
I think you are right about adding the 2 inches before the increases.
As a principle of translating a pattern into “denimese,” if there is shaping coming up, you want to add your extra rows before it starts (in this case to avoid having the armholes placed too high after the shrinkage), and then if it’s shaping that’s spread out over many rows (such as waist or sleeve shaping), you want to distribute your 15% within each little section. So for example, if the pattern says to increase every 10th row, when using denim, you increase every 12th row. It’s ok to be approximate with that 15 percent, so that you’re not increasing in an awkward way, the important thing is that you are spreading the extra length out evenly between the shaping rows.
I wish we could sit together and do this!