you know if i were you
i would just call him out on it
when he calls you names in public be like
" dude that wasn't cool"
or just be more blunt with it
" dude what the **** is your problem ? thinking you can call me out like that ?
you need help "

we all have **** in our past , and its all now water under the bridge . If he cant get over it or is having a hard time just tell him once and
let it be .
live your life and let him figure it out . its not your problem its his .

also don't consistently say
:" why not get some help ?"
say it once andbe done .
if he gets help and doesnt want it , it will be a waste of time . he has to want it