I find it extremely unlikely that it is an exit scam. A week ago or so a member tried to purchase N, and C informed them he's out of stock, and to get back in touch in a couple of weeks. This would make no sense if he was exit scamming.
And low purity N also seems suspicious. C knows, as we do, that he rides on his reputation, and if he cuts it too much the word will spread. At the same time, if we are to believe the account of what happened, it seems like the most likely option. I don't know how much that matters, but I'm 2,5 times the OP's weight, so this is concerning for me too.
When it comes to testing, I am ready to send my sample (obtained slightly more than a week ago through C's website). Can anyone recommend a lab to test it? WEDINOS seems not to accept pentobarbital. I found the International Energy Control in Spain - they seem reliable enough, but testing might take up to 21 days (plus delivery time). As I was planning to take N the week after the next one at the latest, I'd prefer something quicker if it exists. I'm based in the EU.