Sorry to hear about the recent diagnosis, I hope that the stent will make a difference to how you feel. My brother and a couple of friends have had stents and it's made a big difference.
It's not really possible to advise as I'm not a doctor. Obviously you have been relatively successful with a low sugar diet and I expect you have been told to avoid fat to keep cholesterol down. I think that reducing carbs rather than sugars (sugars are a carb) is worth looking into. You'd be surprised how much carbs affects total cholesterol.
The average saturated fat intake for a man is 30gms a day and for women it's 20gms (source NHS). The fat in a 170gm (6 oz) lean steak is about 25gms so a steak would put you over the recommended amount. It might be worth googling a weeks worth of the food you eat presently, just to see exactly how much fat you are consuming. There will be some who can consume fat without it affecting their cholesterol levels. Personally I know my total cholesterol will go up if I consume more fat than usual.
Best Regards