Is there a midpoint between normal eating and anorexia?

Yes, but it's not a very healthy midpoint. See, a person can have all sorts of eating behaviors that don't fall into either starvation, binge-purge, binge, etc. or normal. Many patients with eating disorders have certain behaviors such as eating while feeling good, not when feeling bad. In short, yes, there is a middle ground.

If you're not eating normally but it is not as severe enough to be categorized as anorexia , then i think you fall into the category EDNOS (eating disorders not otherwise specified) or just disordered eating. But even so, you should still seek medical treatment as disordered eating is a sign of unresolved feelings and negative associations with food .

Yes, and this can be found online as well as by speaking to a doctor. You need to be in your BMI based on height and weight.

Yes I believe there is. Many people have restrictive diets or maintain a weight that is less than their ideal healthy body weight for reasons other than psychological disorders. For example those involved in competative gymnastics. In addition to this many people in this midpoint could be in recovery from a restrictive eating disorder or in the process of developing one but do not yet meet the full criteria for anorexia. If your eating habits are impacting on either your physical or mental health/emotional state it is worth speaking to a healthcare provider because 'normal' is so subjective and if there are any issues despite how serious/ non serious you feel they are its worth investigating because seeking help is often the first step to a more fufilled life.

Yes, actually! It's complex and often misunderstood, but there is a thing known as disordered eating. Essentially, you are in between an ED and normal, healthy habits. Ths involves, in transitioning to anorexia, things such as compulsive exercise, paying more attention to calories, warped self-perception.

Not sure what you mean by "midpoint"; there's the normal range of nutrition, and the abnormal range. If you're intentionally choosing to avoid nutrition to lose weight and it's affecting your health negatively, it may be time to consult a doctor.

Yes, there is a line, midpoint which separates normal eating from anorexia. Professionals (psychiatrists from field of eating disorders, etc) know where this line is and they can diagnose you properly. But even they can have troubles setting correct diagnose as some symptoms can be very vague or/and can be integral in many different disorders/illnesses, and so, diferential diagnosis is needed too before diagnosis is set by them for certain. Correct diagnosis is needed for correct treatment. You can't give yourself diagnosis as no one can diagnose self. But for sure, this midpoint between normal eating and anorexia (and any other eating disorders) exist.