This (and I am sorry for your loss).
OP, go to a cardiologist and maybe ask for a referral to a nutritionist as well.
Keto diets are high-fat low-carb. They're good for a lot of conditions (diabetes, epilepsy, some cancers, Alzheimer's) but cholesterol/heart disease isn't necessarily one of them. In general for heart-healthy food you want lean meats and fats (poultry, fish, avocado, nuts, certain oils, etc.) and lots of fiber (veggies, fruits, grains, nuts, seeds). A nutritionist who is aware of your genetic precondition and family history will be best placed to steer you towards the right foods for you. They might also be the one to tell you that foods don't really matter for you and you need medical intervention. If that's the case, that's ok. Take the medicine and develop an ongoing relationship with your medical team (get tested and checked up regularly).