Of course, the key will still be needed to use the car to travel around the world map.
Not sure, but i believe i red somewhere that if you lockpick a car, with a key in your hand, this key would be needed to open the car from there.
No.Once you lockpick car either trunk or door you can automatically use it any way you like as if you had to key, without EVER needing the key again.
After lock-picking just the trunk or just the car I have still needed the key for the other part in my experience.
but you may lockpick both
Make a lockpicker alt (10 INT, 10 AGI, Skilled, etc.) - level it with Flamer against molerats first and centaurs later, get a set of expanded lockpicks and lockpick your car's trunk
:/