i jog 1 hour everyday at 4mph to keep my target heart rate at 70%, and i do 5 set of 20 crunches everyday, will i lose my hard-earned ab-muscles by jogging?

..and what body fat percentage is good for a visible six-pack, im currently at 10%

it's hard to put a number to something like that because everyone stores fat differently. At 10%, though, you should be well on your way to a visible six pack ... you may have to change the type of crunches you do to get a little better workout. As for jogging, you won't need to worry about losing your abs if you continue to work them.