Alright, breeding now is like a game of Yahtzee.
Destiny knot will cause five IVs, selected at random from a random parent, to be inherited. It does not override the power items entirely. If one of the five inherited IVs are the power item's stat then that will come from the parent holding it, when mixed with a destiny knot. However, it does not guarantee that the stat will be inherited with the destiny knot.
Also, with only 3 eggs you have a very low chance of getting what you want. Try at least 10 eggs, 20 will almost guarantee you will find one that you want. A few tips:
1. Do breeding "chains," track the male and female stats that are maxed and try to make them different even if one only has a couple maxed stats as a result. This will save you some time in the long run.
2. Do not be afraid to crossbreed. Find a compatible pokemon with a maxed stat that you are looking for, use the power item on that and the destiny knot on the other. The problem is that you will likely only be able to replace the female with this, so that limits your options.
3. Don't worry about natures right away, you have plenty of time to consider those.