I remember with the first batch I got about a year ago I was able to get it down to just a few chunks on the bottom with a clear solution on top by using 5 percent acetic acid and heating to near boiling and stirring for about 5 minutes. I think you're right and it is the fumerate because that first batch was from a different supplier (though it could have also been the fumerate/same producer, I don't really know; I like the stability, though). I think I could have probably sucked the liquid off the top without getting any clogged and IM'd it, and then just plugged the chunks at the bottom so as to minimize waist (assuming the chunks would have eventually absorbed that way). Vinegar will sterilize the chemical, too, just leave it at 5 percent for a few minutes while heating then dilute it to at most 2.5 percent acetic acid before injecting because it stings (probably not as bad as ethanol, though). You may be able to lower the pH with sodium bicarbonate, too, just add it slowly if you use vinegar to avoid a 4-ho-DPT volcano! Post back if you try either please.
I guess I'm concerned about turning it to a freebase because I'm not totally sure those chunks will dissolve in a basic solution either, at least not with the kitchen chemistry methods I can do. They won't even dissolve in 90 percent DMSO!