You are right that the meanings of these words are subtle and overlapping, and difficult to pin down. Here are the Macmillan English Dictionary definitions for the relevant senses of these three words:

cure: to stop someone from being affected by an illness or to stop an illness from affecting someone.

heal: to make someone healthy again after they have been ill, especially by using methods other than medicine or to make a part of the body healthy again after an injury.

treat: to use medicine or medical methods to cure a patient or an illness.

I think these definitions make the differences quite clear. To cure someone or cure their illness means to make them completely well again, by getting rid of the illness. You can heal a person or part of their body, and this word is used especially when you are talking about non-medical people or methods, so people talk about Jesus healing the sick, for example. However heal is also used about medical treatments, and when used like this it is synonymous with cure, in that it suggests complete recovery. Treat is used in medical contexts, because it refers to the use of medicines or medical methods to tackle illnesses. You can treat someone without curing them: treating is what doctors and other health professionals do when they apply their skills and knowledge to the problems of illness.

So if you are cured or healed, you recover completely, and if you are healed this may be by non-medical methods, but not necessarily. If you are treated you may or may not be cured, but someone has applied some kind of method to your condition.

Here are a couple of examples of each:
Doctors can prolong the life of the victim, but sadly cannot cure the disease.

The patient was completely cured within one treatment.

A drug being pioneered in Britain heals wounds without leaving a scar.

Christ’s primary purpose and function was neither to heal the sick nor to bring relief in other ways.

Doctors treat a dislocation by putting the ball of the humerus back into the joint socket.

24-hour community services would result in patients being treated where they want to be treated.

I had never come across this expression before, but I’m always delighted when someone brings a new piece of colourful language to my attention. None of my conventional dictionaries covers this word, nor does either of my slang dictionaries. Wikipedia reveals that Froot Loops are a kind of brightly coloured breakfast cereal sold in many countries (but not the UK). Fruit loops, meanwhile, are multicoloured rings worn to symbolize gay pride. Wikipedia gives several sexual meanings for the term fruit loops, plus one which I think is the one being used here.

A fruitloop can also refer to a person considered crazy.

A quick search of the Macmillan corpus reveals that the word is extremely infrequent (which is one reason why it would not be in the Macmillan English Dictionary: there are a mere 19 citations for it). Some are a bit too rude to print, but here are a couple:

Why am I a fruitloop and not others?

To me, he remains fascinating, but reads increasingly like a complete fruit-loop.

The corpus citations bear out the meaning that is suggested by the context of your quotation. However, unlike the other examples I have found, the writer you quote is using it as an adjective. I presume that s/he means that the law seems crazy. There are any number of other terms that could have been used, including nuts, crazy, bonkers, mad, and so on.

Interestingly enough, I could have guessed the meaning of this word not only from the context but also from two other rather similar words. One is fruitcake, which is used to refer to a crazy person; the other is loopy, which means ‘crazy’; both are in MED.

I would just point out, though, that all these terms should be used with caution, as many people find them offensive because of the derogatory view of mental illness they imply.