Dad keeps needing surgeries after quadruple bypass?

His heart function was at 25 percent before the bypass once he was strong enough to make it safely through the surgery. Ever since then he has been having issues everyday. He always needs more surgeries. He is only 67 years old and he had issues breathing so he has to go on the ventilator to be able to breath. I called to ask my dad if he wanted all these surgeries but unfortunately he has been incubated so havent been able to talk to him. He has 4 surgeries within a two week period, cant walk and has been diagnosed with dementia. Everyday I have had to make huge decisions on whether to do these surgeries. I approved them because the doctors say this surgery makes it better but afterword he gets worse again. I dont wanna put my dad through all these surgeries because I worry that it will be too much on him. However I'm afraid of making the wrong decision. I get details on each procedure before it's done but when is enough? At what point is it cruel to put him through all these surgeries? My dad told me years ago that if he became a vegetable he wanted to be taken off the ventilator. However he isnt a vegetable and again cant ask when he wants the surgeries to stop cause he is incubated. Mom tells me to stop having these surgeries cause it's too much and I agreed. After I told the doctor that this was the last surgery I'd put him through I hung up. Has anyone had this dilemma with these type of things. I just wanna do the right thing and make sure that this isnt too much.