Listen mate... the numbers are irrelevant... the art of keyword density implies that you should use a specific amount of keywords compared to all other words and when you achieve the "perfect ratio" you rank better...
1. what is that exact ratio?
2. when you come up with a number please show why that is better than any other?
NOTE: dell.com had 0% for years why did they rank better if 2.5% or 5% or some other percent is better?
3. having keyword in title element & page title in Headers and nowhere else - is as good as any other value... and no matter how a page looks stuff with 500 keywords - it will not have any better or worse impact on ranks.
So 75% is fine
50% is fine
95% is fine
100% is fine and so is 0%
And while you said 400 words it still makes no difference to ranks whether 0% to 100% of those words are keywords or not...
This thread been here for almost 6 months... show me "1" noobie that went the route you are so concerned about... if you can't [and we all know you can't] ... your post is pure rhetoric and that means sarcasm equally applies.