How do I get the good ending(s) for Dean?
Technically there's no good ending yet, you have two paths, good one and bad one.
Unless... *SPOILERS*
You meant that he's dying from Sal hand? Or his first death? then yeah you can save him.. I won't gonna give you the password, but one clue.. Find a proper word for a thing that Sal does on Day 11 and you'll be on a good path.
Second clue that word is hidden on a Sal path as well in one of hia conversation with Dave.