I could have written you original post, many years ago.
I was worried sick when my ds got his grades. Quiet and shy. School wanted him to apply for Oxford but ds said no. He was also very young in the academic year.
I was also concerned that his home life was pretty difficult as his father had a severe personality disorder.
When ds started uni I left his father.
Ds went to a local uni on the other side of the city, living at home with me for the first year. Year 2 he house shared, and came home about once every 2 or 3 weeks. Got a bursary, made friends, joined uni clubs. It was afterwards that I heard the stories of uni life and came to know my son as an adult....his escapades, ...... And to learn that although they don't tell mum everything (very little in fact) they actually do become more outgoing within their own circle and limits.... like the night the police were called to their party cos they'd taken all the traffic cones into their house - for a laugh.!!! Police discovered they'd also taken in the crowd control barriers, and gave them 10 minutes to get everything outside again.
Now most parents would be appalled at this. I was just glad to hear he'd been letting the hair down and having fun. He still worked very hard and came first in his course, getting 100%.
He is now a ph.d married to a ph.d, with young son and living a great life.
And as for the quiet boy..... hmmmm.... I wouldn't want to work for him !! He more than holds his own.
As pp said, keep in touch, text randomly....news snippets, and don't expect regular responses. At only 90 minutes distance you could meet occasionally for lunch.- your treat.
And actually it's easier not to worry when they don't live with you.