Help me. =[

Okay so i've had this best friend for about three years, his names Zac. & i've helped him out through so much, and he's helped me too. wel 2 years ago my dad died, and he was there for me, as he shud be, {i lost my dad to drinking and driving} & zac swore to me he wouldnt drink. EVER. now over the past 2 years he's been gettin really racist and angry. he tells me that he hates black people {although thts not the word he uses} and some of my family is black. he also calls all my friend 'dirty mexicans' which is VERY offensive to me in 2 ways:
1-im half mexican
2-my DADS mexican.

hes told me i act like a whore ,and a slut. and tells me im not worth anything in the world but a good b**w j*b. and he actually makes me breakdown adn cry, hes one of the reasons i cut myself all the time. but the next day he'll act like everythings alright.

now heres something thts been bothering me, last week he got really trashed, and told me to get the f**k out of his life. and tht he never gave a sh!t about his promise to me, and tht the only reason why he was my friend was to try to get in my pants {which he did not might i add}

but today he called and told me he was very sorry and tht he needs help with alot in his life, and tht if it wasent for me he'd kill himself.

hes been the best friend i've ever had in my life, but i dont know how much more i can take of this crap hes throwing at me.

i need your advice/opinion.