Mix corn starch and water. It's similar goop. If you slap it, it stays hard, but if you slip your fingers into it, they move right through.
Most ballistic armor is not effective against knives. They use special stab vests where knife attacks are a greater threat than bullets, like prisons. My guess is that a knife would be slender and slow enough to get through the goo.
Broader impacts, like bombs, are generally hard to protect against. Bomb squad guys wear full body suits. Generally, if a bomb throws you, it's also turning your brains to mush.
The best armor around today, type IV, is supposed to stop a 30-06. That's a hefty bullet, but it's nowhere near the power of a .50 BMG.
Any information that's publicly available is probably obsolete.