The point of starting IF#1 first is to get your bowels moving every day. It's the "starter switch" for the whole program. You're going to be releasing tons of toxins, and these toxins have to come out of the body via the colon. If your Dad is moving his bowels every day, then get on IF #2 immediately. The two work together for a really beautiful deep colon cleanse.
Is he on juices only? He needs to be drinking a gallon of fresh juice you make in a juicer every day on top of all the teas and tinctures. I've done the IP with raw food and I'm doing it now with juices, and the juice fast/feast makes the healing go a whole lot faster.
Your Dad WILL get better on the IP if he sticks to the program pretty much to the letter. One thing though- forget the "30 days" idea. Nobody knows ahead of time how long healing is going to take. Just press in and keep going.