Hi, Laslo. Welcome. Observing the enmeshed, enabling interactions of family members is tough. My alcoholic brother lives with my mother. They both have some mental breakdown, and it is really hard to see them together at times. My sib is a total a**hat at the best of times. When he drinks, well, you can just imagine.
He and my mom have a go every once in a while, when she gets fed up with his malarkey.
Do I step in? Do I not?
I have decided that the choice she made to let him live with her (and my father, who died a few years ago) was their choice. It was the wrong one, in my opinion, but it was their choice.
I try to help my mom as much as I can. Basically, though, it's not my circus, not my monkeys.
As sad as the situation is, your grandfather is not going to change his ways at this point in his life, nor will your grandmother. Sorry.
Al-Anon is a really good source of support. Everyone sitting in the chairs has a story similar to yours, and the experience, strength and hope is strong.
Only you can decide if you should stay in the house or move out, stay close or go far away. There is help out there for elderly people, like meals on wheels, and part time caregivers. I would start with my local Council on Aging. Peace.