I'm not saying that glucose provides more energy than ketones on an animal only diet, but that protein is the limiting factor. As one becomes better at using the ketones, they will get more of their energy from fat and I understand that, but it's always reliant upon the protein, so in that sense protein is the primary energy source. However good one becomes at utilising ketones, it's always going to be limited by their protein intake, just to a lesser extent the more adapted one becomes. This means that consumption of meat, not fat, is always the limiting factor, as long as one has body fat(above a drastic minimum level, at which point metabolism shall be limited by both protein and fat). This is of course beyond the minimal quantity of fat one must intake for other purposes. Of course, the way I'm saying, if one isn't intaking enough fat they will gradually lose body fat and will therefore want to increase their dietary fat intake to bolster it, but it's not urgent. Eating fat will not give one extra energy, as their metabolism is only limited by their protein intake in the short/medium term, but fat must be consumed in order to maintain the body fat, which will be used up whilst one is using gluconeogenesis. The body is not worried about using body-fat in the short/medium term, the comfortable range for body-fat is quite large, in comparison to the comfortable range for muscle, as body-fat is largely for storage.
As one becomes more adapted to using ketones, they will not burn more fat... They will only receive a greater amount of energy from the same quantity of fat, thus meaning they do not need so much protein. However well adapted to using ketones for energy you become, gluconeogenesis still requires the same amount of glycerol, and so the same amount of triglyceride, which leaves the same amount of fatty-acid tails being released into the liver, and the same amount of ketones being produced. It's just one's ability to utilise them which increases, so less are eliminated from the body.
This means that fat intake, beyond a minimal amount, is of secondary importance.. You don't need much fat in the moment. Of course, this means that you will eat away at your own body fat stores, but this is not a problem... It just means you need to consume enough fat overall to keep them topped up. Dietary fat, at the moment of eating it doesn't give you any energy, as there's only so much fat which can be present in the blood anyway without causing you health problems. The fat used to fuel gluconeogenesis, the by-products of which are converted to ketones, comes from your stored body-fat, not from the fat which you've just eaten. The protein however, does come from the meat you've just eaten, unless it is not available in which case it will be taken from your muscle. If you are deriving much of your protein from your muscles for an extended period(without taking in protein to form more muscle tissue), you will have a decrease in energy as your body does not want to break down its muscles too much.