The advice for not more than every other day for overweight people is basically for high impact aerobics. This also holds true for deconditioned people who get back to aerobic training. The strategy to be used in these cases is to cross train i.e. alternate between various exercises. This reduces the chances of overuse injuries and imposes a more balanced conditioning stimulus. It is important to alternate between forms of high impact aerobics and low impact aerobics. You should be able to talk comfortably while exercising.
For fat loss, 6-7 sessions per week is comfortable, but cross training is a must. You should gradually increase the duration, intensity and frequency of the exercises. Remember, Warm-ups and Cool-downs (10 minutes each) are a must. In your case, I feel, you have reached a plateau. This means that you are not getting the benefits of exercises as you must as your body has adapted to the changed conditions. So, you must change the intensity and duration of the exercise - Cross Train.
I suggest, you do the treadmill for three days and twice a week you take up some high impact aerobic exercise such as squash, tennis or some other sport you are comfortable with and you should achieve your target of 155 lbs.