nothing strange or abnormal in your feelings ,it's actually quite normal so don't stress about that part.
what concerns me is the age gap. 3 years means nothing when your in your 20s or 30s but at 15 it's quite significant I could understand your parents concerns if they found out.
I think you may have answered your own question in your statement. if it's a one sided friendship and you are getting no support from him it possibly may not be worth pursuing.
hope others have some good advice for you