First of all I would like to say, You are awesome! You have made done so much! Lost weight, decreased your time... WOW. 
I started running back in August using a treadmill. It's great way to start out I think. It helped me with my pace and it was good. Sometime in March I began running half of my runs off the treadmill. I ran on the track. Holy, the first time was hard and I remember that running 4 miles on the flat track killed me. I was sad because I was running sooo slow outside than I was on the treadmill. Back in the day, I would run a 10 minute pace on the treadmill and a 11 minute pace outside. But I kept at it. When I decided to run my half marathon, I started doing my long runs on the treadmill (8 miles) in March and my short runs on the treadmill. Weaning yourself off the treadmill is key, I think. It will take time. But I know that you can do it. When I went home for summer my brother introduced me to hill workouts! I started running all my miles off the treadmill and on the road. There were several things i noticed:
1) the wind is killer...it hurts to push against the wind. I almost died when i ran my first 8 miles off the treadmill. I was lethargic the entire day. laughs
2) the sun is killer...it makes you feel heavy
3) Keeping pace is more difficult..so the slowing down and speeding up makes the run more difficult. ALthough the pace i ran on the treadmill helped me a lot in remembering what a 10 min. pace felt like
4)You can push yourself...you can run faster if need be and slow down on a whim...You are more attuned to your body. This is sorta difficult to do on the treadmill...
So, I agree with the post above..it's best to try to get off the treadmill. I know how hard it is but it's possible. Running on the road is more fun! It is also more interesting. 