I Haven't used "JBL peat pellets" but they should work, (I have used the ones from fluval and regular peat moss from home depot) and If you are going to boil the water I don't think that you need to add any stress coat, besides you are not going to boil several gallons of water, are you? . What I would do is boil all the peat pellets in a gallon or so of water and then add some of that to your tank every time you perform a PWC
as to not lower the pH drastically (if you have soft water), also if you are only looking to get "black water" and are not interested in lowering the pH you don't need much of the solution anyway. I found out that half a cup of a concentrated solution would turn the water in a 46 bow front brown pretty quickly.