Look, I know it's frustrating, but you cannot control brain development. Even if most other kids lost a front tooth or grew 3 inches, would you force your child to lose his tooth sooner or grow faster? Of course not. Because it's not within your control.
Same with this. I think he's doing plenty of other things "ahead" of time. But 31 months is early for most kids, so what's your reason for being so impatient about this? Most kids don't start potty training until 3 years (36 months) and mine was well past the age of 4.
Stop insisting, stop making this a battle, stop making him feel so much drama around the potty. Put the diaper back on, tell him to let you know whenever he wants to try again, and go get out the Duplo blocks or the puzzles and have some fun with something else.
Massaging him to make him pee? Really? Helping him understand the "pee needs to come out"?? The pee comes out just fine - it just comes out in a diaper, as with every other 2.5 year old. Of all the tricks that you say parenting sites have to offer, perhaps you missed the one that says it's developmental and you cannot teach this.
How you get your child to not be afraid is to wait until he is old enough to figure it out. You're forcing him way too early and your obsession with it is just going to make this worse. If you don't want drama when he's 3, or 4, or 5, then stop.