4 Hi Robin,
It sounds like a pretty rough start to the day. I have been there. I only started to learn more about dogs and dog training since September so my current dogs (12 and 13) are not trained.
There is a lot of room for change between positive reinforcement and an e-collar. I agree with Davis that you should review the leadership section on the website especially since you have a young child who is a boy. According to Dr. Brian Hare, Associate Professor of Evolutionary Anthropology at Duke University, 70% of bites happen to children under the age of 10 and more than 60% of the children bitten are boys. 2/3 of the dogs who bite children have never before bitten a child and between 25 and 33% of the dogs who bit were family pets. I don’t say this to alarm you but to keep you informed and so that you know the importance of leadership and obedience.
Following the leadership rules (both you and your son) is a must. Going from positive reinforcement training to the e-collar and doing so without professional guidance can lead to unwanted side effects in your dog. Along with the videos Davis pointed you to, visit https://www.dogtraining.world/?s=obedience for various resources on obedience. There is loads of information on this site. A good place to start is by completing the habitation chart: https://www.dogtraining.world/knowledge-base/house-breaking-chart-habitation-chart/
This will give you a good sense of what Radar needs and when he needs it so that you can follow the leadership rules and provide for him before he demands things.
Good luck to you. Keep us updated on yours and Radar’s progress.