"This means that in the frames of all more distant observers the velocity of any objects approaching an event horizon decreases"
This is like saying the closer one is observed to moving at the speed of light, the closer he looks to not moving at all. His velocity through time is observed to slow as his observed velocity through space increases to c.
Yes, time dilation and length contraction approach infinity in the frame of a more distant observer as the object approaches the event horizon.
The event horizon is the point where the falling observer would be accelerated past the speed of light relative to all more distant observers, which is why objects wouldn't be able to escape from inside the horizon (if they were even able to reach it), because no amount of acceleration can ever allow any object to reach the speed of light relative to any other object which is why the time dilation and length contraction of objects approaching an event horizon approaches but never reaches infinity as they approach but never reach the horizon.
"Objects never reach an event horizon in the frames of any more distant observers,"
You're basing that opinion on the belief that if we observe time stand still in a moving frame, then our time also stands still watching it. Nope, the object makes it to the event horizon (I believe converted into energy) from any outside perspective. Hopefully the guys on here will back me up so the discussion will not devolve.
No I'm basing that opinion on the fact that it's how this works, and this is supported by the standard description of black holes given by physicists.
Of course time in the distant frame is moving normally, but the falling object is becoming more and more length contracted and time dilated as they approach the horizon. If they were to reach the horizon they'd be frozen there, but that would require infinite time dilation and length contraction and an infinite amount of proper time in the frame of the distant observer. If you want to focus on time dilation, their watch continually slows as they approach the event horizon but never stops.
They shouldn't back you up and if they do it will be their own black hole model, not the standard one.
"Regardless of the lifespan of the black hole, all matter remains external so it's kind of a moot point to think about the interior of black holes when no matter can ever experience it."
A gluon is a boson that can be weighed so is it matter or energy? I'd say any type of inbound boson can make it past the event horizon (how else would a black hole grow) so if you consider a boson matter because it can be weighed on a scale, then "matter" can make it into the interior of black holes.
Since science is about trying to understand stuff, I don't think there are any moot points (or infinities that don't tend to a finite value) that are acceptable.
It doesn't make any difference if it's a gluon, another type of boson or anything else. Time dilation and length contraction don;t distinguish between them.
There are conceptual infinities but no practical ones. Time dilation, length contraction, Doppler shift and time it takes for a falling object to reach a black hole all approach infinity as the event horizon is approached by the falling object.