Don't ever leave a guy hanging. That's the shittiest thing you can do.
So respond to him as soon as possible and tell him how you feel.
Don't do that. That's sinister and if see a doctor if I were you.
Better yet a phycologist, therapist. Release all that pent up anger.
If you dont feel enything to him, then just ignore it.
Just tell him how you really feel about him, its probably the best thing to do.