It's hard to say how much goo contains 50mg of DMT because your goo contains other alkaloids as well as plant fats. I don't currently have any goo on hand (I'd post a photo if I did), but my educated guess would be about a third to a half of a US dime.
To weigh it, I suggest weighing your utensil empty first and then scraping up an approximate dose and weighing it again. Then do a little arithmetic.
"Laws alone can not secure freedom of expression; in order that every man present his views without penalty there must be a spirit of tolerance in the entire population." -Albert Einstein
I'm not a big fan of SWIM. I mean, I've never met the guy, but any time I hear about him, he's doing something sketchy.