What I think is the correct way to force feed is attempting to eat even when you don't feel hungry, not overfilling. If it doesn't taste/feel right stop and retry later. That shouldn't give you long term disgust but if you do feel disgust you can stop.
Beef is not strictly required though it's recommended. I sometimes dislike the smell of ground beef but I really enjoyed eating some patties lately. So it seems tastes differ.
Ironically, it could be the lack of fat in grass fed beef. Many people prefer grain finished. It's just a matter of experimentation. There are interesting alternatives like lamb.
Not surprised about your fasting results. That's pretty common experience.