My skin body temp is generally around 35 or 35.5C, sometimes 34.5C, and I don't have problems with it. Remember that your internal body temp is always a bit higher than your skin temp, and that it varies depending on conditions. It could be that even though my skin temp varies from 34.5C to 35.5C, that my internal body temp is always at 36C or higher. In any case, I haven't found this to be a problem. But maybe you're measuring internal body temp, and then it would be pretty low.
A few things that will raise your body temperature are exercise, spicy hearty foods, such as a raw meat+egg+tomato+avocado patee with hot peppers and onion, that I've described in other posts here. Also, a combination of 4/5ths no-salt added, full fat raw cheese and 1/5th unheated honey eaten together will warm you up pretty quickly. Another thing you could try is hot baths. Sleeping with one or more hot water bottles may also help.
During the day, getting direct sunlight on as large an area of your skin as possible will help by allowing your body to produce more vitamin D, just make sure not to get sunlight exposure through a glass window, as that can tan your skin without producing the vitamin D, which is the worst of both worlds because then you will not produce as much vitamin D next time you're in the sun. Actually, tanning is almost always a bad idea unless your regular lifestyle does include spending hours upon hours in the sun every day, and the tanning is just a natural reaction to that. But the way most people do it, which is they take a few days to have intense sunlight exposure and tan, when most of the rest of their lives they have little sunlight exposure, is a terrible idea for their health. If you're in the sun and your skin starts burning even a little bit it's either time to turn around and let other parts of your skin be exposed instead, or it's time to get out of the sun until the next day (or just put on more clothes that cover the affected areas of your skin). Tanning beds are obviously a lot worse. Another trick to maximize vitamin D production and absorption is to not bathe or shower for 2 hours prior or 1 to 2 hours after significant sunlight exposure, especially if you're using soaps. If you shower just prior to sunlight exposure, the soaps and hot water will wash away the cholesterol that your skin uses to make vitamin D. If you shower just after sunlight exposure, they will wash away the actual vitamin D before it's had time to be absorbed. While not in the sun, wearing thick clothes, gloves, etc is also a temporary way to alleviate the problem of feeling too cold.
I would avoid the cooked foods. The heat you get from those is mostly from irritation, not a good healthy source of warmth. But yes, cooked fatty meats eaten in abundance will raise your body temp a lot. So will a combination of cooked starch and cooked cheese, such as pizza, or rice/pasta with plenty of hard cheese. Or something like spaghetti and meatballs, especially if it's really fatty. Again, I wouldn't recommend these. The reason they make you warm is because they put your body in alert mode. Also because raising the body temperature helps deal with some of the toxins and the cooked fats, and helps keep them liquid and more malleable, easier to carry from one part of your body to another, and easier to be utilized and converted into something less harmful.
The beef fat you ate, was it from grassfed beef, or feedlot beef? If from feedlot beef, the reason it made you sick is because of all the toxins. If from grassfed, did you eat it alone or with muscle meat? Force feeding only meat fats can overwhelm your body, especially beef fat. Pork fat is more mild. But both should be eaten with about an equal amount of muscle meat at the minimum, especially if eating them in large amounts. Allowing your meats and in particular your meat fats to reach room temperature or be slightly warm when you eat them will also improve digestion and taste. I usually can't be bothered and just grab something and eat it cold off the fridge, but if you're having problems then consider doing one of those. Some people sun-warm their meats prior to eating them. A closed glass container will work great for this. Just make sure not to let them sit in the bright sun for too long while inside the container, or they may begin to cook.
I'm sorry to hear about your husband. I can't imagine what it must be like going through something like that, and dealing with the aftermath.
Did he have an illness? And was he eating mostly raw like you?