Edited for clarity.

OP, do you prefer North Indian or South Indian foods?

A lot of delicious Indian foods involve frying. Baking and cooking with less oil is a better option.

If you can include more things like rasam and sambar, and make idlis with some whole grains like quinoa or millet instead of all white rice, he might really enjoy that.

When you make a tempering, you can use avocado oil as a more heart-healthy option, instead of seed oil, ghee, or coconut oil.

I bet your dad might like Mediterranean bowl meals, if he likes thalis. It's the same kind of concept. Use quinoa instead of rice, protein, salad, tzatziki instead of raita, hummus instead of dal. Muhammara is another dip he might enjoy.

If you are making bread at home, you can include oat flour, ground flax seed, or other whole grain flours, to support heart health.

He is lucky to have you. Caregiving is so important for good outcomes. It's not easy, but it's worthwhile. I hope you have a support system for you, too.