Keep running, it works. I would suggest the intervals twice a week. I am not as fast as you. I do about 11:30 mile pace, but I run hard for a minute and walk for a minute most of the time. I am doing a pretty strict 1800/day diet. I only think I've gone over that two days since April 12, and even then, not by a lot. The weight is falling off of me (300 lbs. to 222 lbs in just over 4 months).
I am coaching cross country and that makes it easy for me to run. Those guys and girls come out thin and they all show off how loose their jeans have become at the end of the season and I watch them eat 4000-5000 calories a day. They run long distances (5-10 miles) 5 days a week and do the intervals twice a week. Of course, they do them much more intensely than I do, but after three months of cross country there's not a muffin top, or a hint of cellulite on any of them. I'd bet the body fat numbers are ridiculously low. Heck, we're one of the worst teams in our area.
I think what you're doing will work. Stick with it, add the intervals, maybe. One thing is you're probably getting more solid. You slim down a lot running, but your body needs muscle to run so what you've got becomes muscle. Once again, using our runners as examples, they're all amazed how they end up with six pack abs and super defined muscles and legs after just three months of cross country. Frankly, they're a little conceited about it.
Started at 300 lbs., now at 221, going for 150.