Your friend’s attitude toward people who are Muslim is outrageous. Bigotry is never a good basis for making choices. However, your boyfriend’s situation with his visa shouldn’t force a premature decision about a lifelong commitment.
The smartest thing you said is that you wouldn’t marry him yet regardless of the court’s decision. You are only 21 and you’ve only known your guy for 5 months. That’s not enough time for a relationship to mature to the point of considering marriage.
Many couples are separated by jobs, school or circumstances. Skype, texts, and email keep them talking and keep them close. Regular visits now and then help them get closer. Over time, they are able to decide if the relationship has real promise.
In my opinion, you two should enjoy your love and spend as much quality time together as you can. If he has to go back, he has to go back. How you each handle the separation will tell you what you need to know about whether your love can last.
I wish you well.