Bread – make the own malt

I wouldn't replace milk powder with vital wheat gluten. Vital wheat gluten changes the gluten content of your recipe. It's good for, say, turning whole wheat flour with a lower gluten content or AP flour into flour suitable for bread.

When I add vital wheat gluten, I subtract flour as your friend does. I only use it when I am not using a high protein flour.

The dried nonfat milk powder is likely in the recipe for flavor. I would instead use milk in place of water and either up the flour as needed or replace with flour as needed (you can tell this during kneading). I've done this just fine in bread recipes before.

I use whole grains in my bread- wheat, oats, quinoa, etc.

There are a couple considerations: 1- rehydration If the grain won't be adequately rehydrated from just sitting in water for an hour then it should be precooked. Wheat berries, for example, definitely need to be cooked. They just won't get enough water or time in the dough while it is rising.

A little experimenting may need to be done to get the water ratio right.

2- sharpness Adding hard ingredients will change the dynamic of your dough kneading. For example, if you knead in a mixer then you might have to go at a slower speed to keep from shredding the gluten.

Sprouting grains is fantastic. Sprouted grains are very nutritious and have a completely different flavor that I find very interesting. Sprouts also have a lot of sugar in them. I sometimes replace some of the sugar in my recipes with sprouted, dried, and ground wheat berries.