Whats A Normal Muscle Percentage For Women What Can I Improve On To Lose Fat All Around, Without Losing Muscle Mass?

What can I improve on to lose fat all around, without losing muscle mass? - whats a normal muscle percentage for women

Okay, so here's the biggest part of my education:
Monday: upper body (arms, chest, back, etc.)
Tuesday: lower body (thighs, quadriceps, thigh adductors, glutes, abductors)
Wednesday: Like Mondays
Thursday: How to Tuesday
Friday: How Monday and Wednesday
Saturday: How to Tuesday and Thursday
Sunday: Closed

Before starting work each day, I do 20 minutes of high intensity heart on the treadmill.
Since I started, I gained a little muscle and lost some body fat. I am satisfied with my result, but I have trouble losing fat in my area of the buttocks and abdomen. I have lots of belly fat, but enough to cover for my six pack. But I have enough fat in the buttocks that were found (a little)
My questions:
How can I lose weight without losing muscle mass? Because I do not want my work goes down the drain, but I want a low percentage of body fat.
My body: 152 pounds, 6 feet (before you say I'm too thin and not lose weight, I amAll bulky. But I take all the precautions adopted, not with the Stamp 150 to go. I used to be about 165 pounds in the summer is not much muscle mass)
My second question is: I know I am a normal weight, as it is, but it would be a good weight for someone 6 feet tall? 145 is too thin, even with a little muscle mass?