Thank you for your email. I understand you are feeling angry that you have had to act in the best interests of your daughter against your beliefs. You did the right thing and your daughter needs your guidance, knowledge and support now more than ever, especially if her relationship with this young man ends.
Continue trying to get to know him and his parents by phoning them and possibly inviting them around for tea. Research indicates that most teenagers are either thinking about or engaging in sex and by talking to your daughter and her boyfriend you can help them make the right choices and engage in safe sex as well as have respect for each other.
As you daughter's boyfriend is a 'nice' guy, appeal to his sense of responsibility as the older teen, especially when you feel uncomfortable about her curfew time, and always explain your reasons why you are creating rules and boundaries. Ask him what his intentions are with regards to this relationship moving forward when your daughter is around. Does he see them being together forever or only for a while. Ask the questions your daughter may not have thought of so she has a clearer understanding of how he feels and his intentions.
When chatting to them try to put your anger aside so they are able to tell you how they really feel without you exploding. Talking and educating your daughter is empowering her as she will have all the knowledge she needs to make the right choices, and it will also make it easier for you to trust her. It is important that you chat to them about using condoms as well as the pill and sexually transmitted diseases.
You don't mention your daughter's father but if he is around he should be involved in setting boundaries and chatting to her boyfriend and his family.
Have a look at the site www.scarleteen.com/for_parents for more support and information.
You have not abandoned your daughter as many mothers would, and while instinctively it is harder keeping her safe and you have to let her go a bit, it doesn't mean it should impact your relationship with her negatively.
Good luck and let me know how you all are doing.