I'm sorry you're dealing with this. Having a financially irresponsible parent creates real anxiety, and you deserve clarity so you can plan your own future. Here's the good news: You are not responsible for your father's debts when he dies. Period. Debts die with the debtor unless you've co-signed loans, have joint credit cards, or are a joint account holder. Don't do any of those things.
As a planner, we typically come up with a strategy, and we use attorneys to actually draft the documents. In 2012, my wife's grandmother passed away, and I was nominated as the executor. And as anybody that's been in that role can attest, it's one of the worst things that can happen to you. When you are the administrator, trustee, you're never asked your opinion when the document is being drafted.