THE MAJOR mistake made by virtually ALL researchers and people taking [so-called] vitamin C is inadequate dosage(s). If they took only one-half [or less] a dose of Antibiotics , would they expect to get a positive outcome? And yet somehow the VAST majority "test" ascorbic acid with a few grams [or less], and when they do get an immediate amelioration of the[ir] symptoms, they assume it is of no use. Do not make that mistake!
As the article points out [and implies]: Let the body "decide" how much it want/needs via its passing the unabsorbed ascorbate on to the colon [for excretion]. Not until then do you know you have had enough [FOR THE MOMENT].
As "grist for your mill" Eric, MY Bowel Tolerance is WAY more than you've tried, and I have virtually perfect health.
Your health issues did not develop over-night, and their [true] solution will not come over-night. I have taken Bowel Tolerance doses of ascorbic acid for nineteen years [in health, virtually never illness], and intend to do so for the rest of my life. I believe we ALL need all of the antioxidant(s) we can possibly get [and my study and experience in the matter has convinced me that ascorbic acid is simply the best supplemental source available]!
I use Kirkland Signature from Costco [because it is the least expensive that I have found], but as long as the filler in your tablets [usually the second item listed in the ingredients list] is NOT calcium carbonate, I assume any tablets will do. HOWEVER, make sure what you are ingesting is ascorbic acid, and not one of the mineral ascorbates, for the simple reason that gram-for-gram, it is literally twice as potent as the mineral ascorbates.
If you have any [more] questions and/or concerns, you are most welcome to let me know.
Best of success to you, Eric!
P.S. If ingesting ascorbic acid makes you feel worse, it is [virtually] a GUARANTEE you need it's cleansing very badly! My advice is simply to moderate your intake to a level where you can live with the cleansing.