That's very hard to deal with and my heart goes out to you. I went through a similar situation with my mom. She had Alzheimer's for about 6-7 years before she passed away. In the last few years her swallowing started to deteriorate gradually. When I went to see her it was always during lunch or dinner time and I'd feed her in those last years. Sometimes she'd choke on her food, so they started thickening her liquids but she didn't like the taste of them and made faces or pushed it away.

She never got to the point of a feeding tube because in her situation it would be considered life support and she didn't want to live like that.

But maybe your dad has a chance to recover his swallowing ability over time? I don't know much about heart attacks. My sister had a mild one in the springtime when I was out shopping with her but she seems to be doing ok now, though she hasn't lost weight and I'm afraid that will cause another attack if she doesn't.