I think that by forcing less, you will gain more.
Start by telling your oldest son that you're sorry you've been insisting that he attend sporting events. That's something that parents do, not college kids who work full time in an emergency room. Don't just drop that request: address it clearly with your son and tell him that sporting events are now off his to-do list.
Then, make sure your oldest son has a place to relax. I hope he has his own bedroom. Let him relax as much as he wants, or study alone. WiFi in his room, and a place to sit without interruption from younger siblings. Everyone knocks before entering his room. Make that clear to your younger kids.
He's not responsible for your daughter's movie reactions. She's 10, right? That movie is PG-13, if I am not mistaken, and if she is watching an emotionally charged movie about such a serious and tragic event, then it is your responsibility as her mother to either watch it with her, or address any emotions or feelings or questions that arise. Your son is not a parent; he can't be expected to respond with a parent's unconditional love and with the patience that years of parenting brings when a young child feels upset.
Let your oldest son know how proud you are of him, and let him know that you've been expecting parenting behavior from him when he should be a student and an ER staff member and he should be acting like a 20 year old with no kids.
That does NOT, however, exempt him from being a basically polite human being and member of the family. Remind him that it is his choice to live at home, and home includes parents and siblings, and a home functions smoothly when there is respect - both ways. Lay down some basic expectations. You will require less "parenting" behavior from him, and in return he will simply act respectfully towards others in the home. If he eats food in your kitchen, he washes his dishes or puts them in the dishwasher. If he uses your washer and dryer, he doesn't leave wet towels on the floor or dump his laundry on the floor in front of the washer. If he has a full day of classes then a full night of work, and if he needs some clothes washed or a lunch packed, he's to ask you politely. Otherwise those things will be up to him.
Don't expect him to watch tv in the living room, or use his computer in the family room. Ensure that he has privacy and the privileges of being a good college student and effective medical team member.
Say what you expect from him, and say what freedom he has earned, aloud. Don't just assume that by not inviting him to next week's soccer game, he'll get that he doesn't have to go. Be clear, and be respectful.