What drugs is he on? He really needs to go to a rehab inpatient. It will get him clean, if he goes to NA OR AA after the treatment that helps alot. Sometimes for people it takes afew tries of getting up and falling back down, depending on the drug its not an easy road for most people to get clean. I wish for you and your father to be strong
Your dad must take the steps necessary. All you can do is to involved yourself in Narcanon or Alanon, family programs for the addicted loved ones. You must learn what you can and be informed. Then if he wants your help, you'll be well read, and well versed. I'm sorry that you're missing your dad, and i'm so sorry that you have lost your mom, and he has lost his wife. After going to Alanon, you can let him know that you've gone, that this is what people do , they reach out for the hands of those who've been in your shoes, and have survived, and thrived. as best we can .
It is a long road back from addiction, there is nothing that is going to happen overnight, and with the help of Alanon, Narcanon, you can face these challenges with the people that you might become close to.
Thanks for posting and let us know how things are going. God Bless.If you ever want to talk to anyone here on medhelp please feel free to reach out.