Visually, we see the bolt stop. Perhaps Kylo Ren didn't stop it, but was using all his concentration to SLOW it down. Of a Jedi trying to lift an object must still combat gravity in their attempt to lift something, then why wouldn't the velocity of a blaster bolt be combated and continue along its initial path?
I'm okay with new force abilities, as long as they fit in with the overall previously established view of the force. If a force user could teleport, or fly through hyperspace without a ship, or turn invisible, I would think it was pretty stupid. The biggest problem with the blaster bolt is that it then continues on its original motion once released. If it just fizzled away, deflected, or exploded in place, that would have made more sense. Why even use lightsabers to deflect blaster bolts if you could control them with the force? If he is stopping time in some way, then why would Vader and Palpatine not freeze Luke in place rather than the whole elaborate carbonite plan? And if you say that Kylo is THAT much more powerful than Palpatine....
Why wouldn't Palpatine and Vader do it? Perhaps they didn't know how, or bother using it. I'm sure Kylo was using his full ability of the force to keep that bolt hovering. Kylo DOES have Vader's blood in him. Who knows how strong he could be. He isn't focused enough to keep his control.
Forward momentum cannot be stored... a.) either the bolt has mass and velocity, in which case slowing it down would decrease that velocity, and when released it would fall or travel forward at its current velocity, or b) the bolt is still traveling at the same velocity but somehow time has slowed for the bolt itself. And sorry, if 20 year old Kylo Ren is more powerful than Palpatine at his prime, then the story falls apart. All of TFA was done with the mindset that bigger - stronger - more dramatic - more diverse instantly translates to better - cooler - money. They don't bother giving reasons, they just assume we won't question it because it's so much more badass.