About Parkinson's disease, here are a few thoughts.

• All diseases are only the consequence of wrong thinking/detrimental beliefs, therefore going to the root of the problem would be the most rigorous procedure.
  I know someone (not in person, but a good friend of mine had excellent results through him) named Ed Strachar. He is a healer, and from how he describes his healing method, he goes to the root of the problem, which is always located in the soul of a person, and the disease is nothing but the manifestation of the wrong thinking.
  In any case, I think you should check him out, and see if your step-father is receptive to this type of healing. His website is https://healinggenius.com/, he is on facebook (I am not), and if you google his name, you will find him. Just a warning: His services are quite (I should say - extremely) expensive, but he also does a lot of charity work.
  Maybe you resonate with him, and he is someone who can help your step-father.

• I didn't know about PEMF until now. My first impression was that it reminded me of the implantable devices (deep brain stimulation), and even though results with these are impressive, I definitively would not proceed with such an invasive method.
  However, PEMF apparently can be applied anywhere on the body. This is quite interesting! I had the impression that mainstream science treats Parkinson's mainly as a disease of the brain/neurons, specifically neuron death and as a consequence lack of dopamine. (Which is specifically treated with a certain type of medication.)
  The fact that applying PEMF to the feet or the hands is effective obviously shows that this view is not complete, maybe even wrong. (Wouldn't surprise me...)
  My personal (cursory) verdict about PEMF (based on the article): Looks like a good method. Open questions are: How long do the effects last? Is it something that is always effective, or does its efficacy wear off over time (for instance, because too many neurons die off anyway - then maybe another method should be used to prevent that).
  Is the application for longer periods of time worth it? Meaning, would your step-father be able to be away from home (without the device) for longer periods of time, or would he be "tied" to the device?

• Methylene Blue (MB): There is A LOT I could write about this! Here just a few points (simplified): MB provides the energy (electrons) for the mitochondria to function better. (Krebs cycle/citric acid cycle is the relevant key word here.) Mitochondria are present in ALL body cells, but they are highest in concentration in the neurons. By ingesting MB, one provides the mitochondria with "more electrons". It stands to reason that this improves the performance of neurons, and thus diminishes the detrimental effects of any disease such as Alzheimers and Parkinson's, which are caused by the degeneration of neurons.

An excellent researcher is Dr. Francisco Gonzales-Lima, and I highly recommend these two podcasts:

Methylene Blue: Part 1 with Dr. Francisco Gonzalez-Lima

Methylene Blue: Part 2 with Dr. Francisco Gonzalez-Lima

As to the practical side (always referring to the 1% solution, unless otherwise stated):

• One should start with one or two drops daily, and slowly increase dosage until the end dose is reached. (Approximately 1-2 drops more per day, but always watch for negative effects, particularly Herxheimer reaction.)
• Take for six days, pause one day.
• Extremely important: MB is effective in low doses, and damaging in high doses. (In general - there are some treatment protocols that deviate from this, but mainly in a clinical setting.) Low dose is 0.5-4 mg of MB per kg of body weight.
• It is a bit cumbersome to handle. One has to measure out a certain amount of drops in a glass of water. (Possibly difficult for someone with hand tremors.) Since it is a liquid, it cannot packed in capsules.
• There is one company that makes so-called "troches" (troscroptions.com). These troches are to be put between upper cheeck and gum, the substance is absorbed throught the oral mucosa, and goes directly into the blood stream. This might be easier to take than the drops. Downside: The mouth is going to be blue, VERY BLUE!
• There are a number of companies that sell the 1% solution, especially in the US, where it is more freely available (I think). When it is declared as "USP" (=United States Pharmacopeia), then it is certainly OK (such as in your example). That is the label for substances intended for human consumption.
• For an "average person" of 75 kg, the minimal daily dose might be around 75 drops (1 drop of the 1% solution contains 0.5 mg of MB). That's rather annoying to measure out on a daily basis... Therefore:
• Buying MB powder and making a solution with a higher concentration is advantageous. I have a list of companies, let me know if you're interested. (It's probably only of interest once you have tried the 1% solution and want to continue.)
• Powder is certainly less expensive, in the long run.
• It is blue, VERY BLUE! In higher concentrations it will stain your mouth. If you don't like this, drinking with a straw might lessen the effect. Also, be cautious not to spill on things you do not want to be permanently stained. Stainless steel in the kitchen should be easy to clean, though.
• It is not only for patients with a neurodegenerative disease, but also for "healthy" people to be used as a nootropic. I personally use it (though I have issues with energy levels, and that's my main reason.)
• 0.5 mg per kg of body weight is not necessarily the minimum dosage, I've read that some take much less. It seems that that the effects related to dosage may vary from person to person.
• Preferably take it in the morning, not in the evening. I've tried to increase my dosage, but dividing it up into two portions (morning and evening), but started to have considerable sleeping problems (and sleeping problems are definitively not one of my issues). It is probably because of the stimulating effects, not sure. Maybe not everyone reacts the same, you'll have to try out.

The remark "This Product is Sold for Research Purposes" is a bit strange indeed. I suppose it is for liability reasons. USP means "United States Pharmacopeia", meaning the product is according to the US regulations for pharmaceutical products, meant for human consumption. But the seller here is in the UK, so I assume he buys the product from the US, but strictly speaking he can't use "USP" - because he's in the UK, not the US... In the end it is irrelevant, as long as he is really selling an USP product. Which means, the product has a very high purity (99.7% or so), defined in the USP books.