It sounds like genetic testing will be the best way to sort this all out. Most doctors have had so little experience with any type of myotonia that if they see a positive EMG they immediately think myotonia congenita.
Does anyone in your family have symptoms similar to yours (even extended family)? Even with the dominantly inherited forms of myotonia it is possible for parents to appear to be asymptomatic. But if no one including aunts, uncles, cousins, grandparents, etc have symptoms, then it is more likely a recessive form of myotonia. Also with myotonia congenita we almost always have symptoms beginning in childhood, usually from age 2-12. The stiffness and muscle hypertrophy can be quite pronounced even in toddlers.
Muscle biopsies are almost always inconclusive for us. I don't know why doctors still put patients through that when DNA testing is so readily available. There will almost always be atrophy of Type IIB muscle fibers in myotonia congenita. I'm not sure if that is the same as the necrosis in your report.
One possibility is that you may have a condition called Isaac Syndrome or Neuromyotonia. That would explain the muscle pain and cramping as well as the myotonia. In most cases this is caused by antibodies to the potassium ion channels. Wikipedia actually has a good overview: Neuromyotonia
I don't believe neuromyotonia is specifically associated with gallbladder issues, although CK levels can be elevated. The high CK (and I have seen it even higher than yours with myotonia) is a result of the muscle cells being damaged. Bodybuilders always have elevated levels for a day or two after an intense workout. It all depends on how much the muscles are stressed. When we push against the myotonia (for instance when our legs suddenly stiffen as we're going up stairs) it will simulate extreme isometric workouts so people can have quite pronounced tissue damage.
The other condition that comes to mind is myotonic muscular dystrophy or MMD. There are two types, DM1 and DM2, and possibly a third. Myotonic dystrophy is associated with GI issues including liver and gallbladder problems, as well as cardiac problems as the condition progresses. A simple screening tool at your age would be an eye exam. There is a very particular type of cataract seen in myotonic dystrophy, sometimes referred to as a Christmas Tree cataract. It can begin to form in the 20s and 30s and often this is the way many people are initially diagnosed.
Elevated liver enzymes are not related to myotonia congenita, but they would definitely be seen with MMD. If it was inherited from your father, you may not have symptoms until adulthood. Often if it is from the mother, the baby will be born with poor muscle tone and a much more serious form of the disease. It is possibly to have hypertrophied muscles earlier in life from the myotonia, then they begin to atrophy as the condition progresses.
I don't believe I have known anyone personally with MMD who had the pain/fasciculation attacks, so it's very possible you have a combination of two disorders like neuromyotonia and a liver/gallbladder disease. But in any case, DNA testing for the myotonia congenita and myotonic dystrophy will confirm or exclude those. The testing for neuromyotonia usually begins with antibody tests, but that is not always conclusive.
For now I would suggest using 1000-2000 mg of the amino acid L-Taurine. This will help with the gallbladder issues and will also relieve some of the myotonia. For the muscle cramping, magnesium citrate is a good supplement if you're not already using magnesium. Too much will increase potassium to the point that it may affect myotonia, so usually 500 mg is a good target.
The other two supplements I would recommend are milk thistle extract with standardized silymarin content (liver support) and Acetyl-L-Carnitine for muscle support. Also medium chain triglycerides are less likely to cause muscle cramping and liver issues. I would ask for a carnitine related mitochondrial disease screening to be sure that's not a factor in the elevated CK levels.
I'm sure you're a bit overwhelmed with all this, but at least you have a clue (myotonic discharges) to start narrowing down the possibilities.