You might need to be careful with Methionine as it can be a problem for some people, therefore do not take too much too quickly. It might be best to slowly increase the dosage of all of the Glutathione amino acids. Be aware that Glutamine and Glycine can have a sedating effect, Glycine certainly does on me. I use L-Aspartic Acid to try and balance this as those four aminos are essential to Glutathione production.
You might also look at the foods which increase Glutathione production. Garlic is meant to have a positive effect in this regard. Milk Thistle extract is also meant to have a strong effect on Glutathione production and liver protection. There are others which I am sure you can find easily.
BTW If you intend using Whey, then I suggest that you stick to liquid Whey and drink as quickly as you can. Avoid any protein that you have to chew. Save your chewing for vegetables and fruit. That is based upon what I know of the causes of CFS.