okay, im a lil young but maybe i can help. its obvious u want to help him and appoligize to him sou should really do that.
try to get really calm and contact him. i would say in person. but make sure he wants to talk. if u have to, make him talk to u. but dont be mean.
i've lost close ppl so i know how it feels. its really hard. he may just be pushing u away bc hes really emotional and he doesnt want u to see him that way. he obvilious loves u since u two were suppose to get married.
now, just get calm and say ur sorry, and make sure to let him know that ur there for him. thats reallly important for him to know. but overall, u need to do what feels right.
best of luck and i hope everything works out fine.