I sympathise. Not same kind of family stress, but last 2 years or so have made me quite anxious. Health worries with daughter's partner & their youngest daughter. They live 400 miles away, which added to the stress. We couldn't help them as readily as we could have if they'd been nearer.
I ended up getting tablets from doctor & had CBT to help deal with it. We worry about our kids, no matter their age. Mine are 30 & nearly 35 & I worry.
Exams are so stressful for youngsters these days, so much pressure is put on them. Teenage romances can cause all sorts of problems too. Be there for her, shoulder to cry on, whatever it takes. I'm sure you are already.
Some career advice might help your son, although don't remember it being much use to me. Our son didn't appear to have any idea when he left school. However, we were on holiday & phoned home to see if all was OK. Turned out he'd gone along to an open day at local college & signed up to do a mechanical engineering course. He got a job after college in marine design & has been there ever since.
My mind races, especially thinking of "what if" scenarios. Part of my make up, or so hubby tells me. Some days are an effort for whatever reason. I don't go to work though, which helps. How some ladies manage work at this stage of our lives, I don't know. If I was still working I'd be a wreck.
Sorry that probably isn't much help. But at least you know you're not alone.