The science isn't really all over the place. Vested interests are creating studies to attempt to sew doubt with the public, just like the tobacco industry did in the second half of the 20th century. Here's an example: want to create a study that tries to debunk cholesterol being bad? Create a study where everyone eats the same amount of cholesterol, measure their cholesterol, note that they all end up with different amounts of cholesterol, and declare that there's no correlation. That's the kind of science that the dairy and egg industries are famous for. But it's junk science: everyone has different starting levels of cholesterol because of genetic differences. However, if you reduce cholesterol in people's diet, you get a drop in bad cholesterol. If you increase the cholesterol in people's diet, you get a rise in bad cholesterol. Open and shut.
Independent science, not funded by vested interests, shows a consistent narrative. Cholesterol is bad, saturated fat is bad, excessive amounts of animal protein in the diet is an anti-nutrient due to it overwhelming the liver, etc. Vested interests are becoming increasingly brazen in creating junk science to convince people to buy their products, so government health agencies have had to start ignoring all industry-funded science in coming up with health recommendations (as the Canadian government recently did when updating the Canada Food Guide, as one of several recent examples).
You really don't have to look any farther than this: the healthiest and longest-living populations are the most plant-based such as the traditional Okinawan diet (98% plant-based), the Adventist vegans (100% plant-based), etc. The adventist vegans are the longest-living population ever studied by science. And these populations not only live longer, they have a reputation for being vibrant in their old age (aging okinawans doing tai chi, aging adventists mowing their own lawns instead of being in nursing homes, etc.) People can debate theories until you're blue in the face, but when you put it to the test the more plant-based a population is the more likely it is to thrive.
That's the thing several things you have said here have already been debunked by scientist. I heard 3 hour interview where a scientist went over all of this and she had no vested interest. Do you have a source the "The adventist vegans are the longest-living population ever studied by science" Couldn't find it online. Also stuff like this isn't science so we do have to look further. There is a process and a way things are done in the science community and they are done that way for a reason. Just going "look at them over there, do that they do cause it worked for them" isn't science.
In fact that was one of the main complaints during that 3 hour interview is how horrible studies are being done and it made me realize that you can't just read a studies headline you need to get into and see how it was done. She broke down one of those vegan documentaries and verified all their sources and went through each study in their source and broke down what the issues were with the study. One of the studies used by the american heart association was literally just a survey. Do you eat meat? Yes or No. They then used that data to decide if eating meat increases heart disease, etc.