Given that you’ve gone straight to carnivore from the standard American diet (SAD), be aware of a couple of things:
First, the adaptation to a carnivore diet is bad enough for someone who has already adapted to a keto diet, so you are in for a bit of a ride. This is completely normal, and will pass. But give carnivore eating a good six-month trial, before deciding it’s not for you. And remember the advice of many long-term carnivores: practically everything a beginner experiences can be solved by eating more meat. Don’t fast, don’t count calories, and eat three times a day. Give your body what it needs to heal.
Second, the kidneys excrete sodium more readily in the absence of insulin and glucose. This is normal, and all you have to do is to boost your salt intake a bit. Long-term carnivores usually find themselves dispensing with added salt, and you may too, eventually, but if it happens, it won’t be till much farther down the road. If you are getting enough salt, you may or may not need a magnesium supplement, but but don’t shy away from taking one, if the cramps continue after increasing the salt. Eventually, you will probably be able to dispense with it.
Third, with no carbohydrate in the picture, the skeletal muscles must reactivate certain metabolic pathways in order to use fatty acids as fuel. In the meantime, they will manage by metabolising ketone bodies. They really prefer fatty acids, however. This need for re-adaptation is the reason for the muscle weakness. Don’t overstress your muscles for right now, but you should gradually feel your strength and endurance returning over the next several weeks.
Fourth, as far as our sleep is concerned, we do not need to sleep a specified number of hours; we need to sleep long enough to waken refreshed and energetic. If you are wakening rested and refreshed, then you have no problem, except the one of figuring out what to do with the extra time. If, on the other hand you are not wakening refreshed and rested, then just try to cope for now; it will get better later on. Your body is making several major readjustments right now, so give it time to sort itself out.