You really don’t need to worry about meeting macros. These are percentages calculated off total calories, and for one thing, 20 g/day of carbohydrate is an upper limit, whatever the percentage of your total calories that works out to be. For some people, 80 calories of carbohydrate might be 5% of their calories, for others, a higher percentage. So just go by weight.
Second, as others have mentioned, the amount of protein should be reasonable. Most people eat somewhere between 1.0 and 1.5 g/day/kg of lean body mass, and some go as high as 2.0 g/kg. So eat what feels right, and don’t worry about it. Since meat is only about 1/4 protein, this actually amounts to more meat than it seems.
Third, fat is an excellent source of replacement calories for the calories you are no longer getting from carbohydrate. You don’t need as much fat, because it has over twice as many calories per gram (9 cal/g) compared with carbohydrate and protein (both 4 cal/g). If you cook with butter, tallow, lard, or bacon grease, that will not only add fat to your diet, but will also make your food taste scrumptious. You can make delicious sauces and gravies with heavy cream to pour over your meat and your vegetables.
The key is to eat enough fat to satisfy your hunger, no more, no less. Trust your body to tell you when you’ve given it enough. So you see, macros are hardly necessary. Just keep your carbohydrate low, eat real food, and satisfy your hunger (don’t eat if you’re not hungry, either). You don’t really need to calculate macros or count calories—unless, of course, doing so gives you real pleasure.