Purchase the book "1-2-3 Magic" - all of the book stores carry it! Your library may also have it on video. It works wonderfully! My sister recommended it to me many years ago - a therapist recommended it to her with her son who had issues due to developmental delays.
Funny thing... I will still use it on my teens out of old habit and it still works!
Hint: your husband needs to be on board with the same discipline approach or else no discipline plan of action will work effectively.
He is clearly having a hard time with "transitions/change". He has no clue what 5 minutes means. You need to speak in his language... when that tv show is over or when we are done cleaning up the toys we just played with it is time to leave.
Ask him how he feels - "Does it make you feel sad to have to leave your friends house when you are having so much fun here?"
Wait and give him the chance to process his thoughts and allow him to speak.
Affirm his feelings - "I understand that you want to stay longer and that you don't want to leave."
Read books to him that talk about their feelings - great thing to do while feeding the baby! Try to find things to do together, with the baby too! Make the baby seem like she is fun to him, not some blob who just takes up his parents attention - take her hands and have her "wave" to him, "tickle" him, when you are playing a board game - have her hand help you move the pieces so it seems like she is playing too. She will definitely become more exciting to him in a couple of months. Make sure that you allow him to hold her - try laying next to her on your bed and watching his favorite tv show is a really great bonding experience they can do together - just prop her up next to him and you can put away laundry in the room at the same time!
Remember... this time of craziness shall pass! Give yourself and your son some grace here! He is only 2 years old... enjoy him and your newborn daughter! Thank God every day for your lovely family and their health!