It's hard to take it much further if you refuse to accept the facts that seem improbable to you.
"Yes, masses are present, but they are not to the degree you require." You state this without saying how much mass is present and exactly what degree it is you think I require.
Let me jump in and offer that these clouds of particles would have a mass on the order of trillions of solar masses. Just how much mass do you think it requires?
"A sparse cloud of dust exerts next to no force on its outer reachers[sic]..." A sparse cloud of dust exerts precisely the same amount of force at its outer reaches as it would were the same amount of mass compressed into a single point at the center of mass of that cloud. Here is Gauss's Law. This is a rather nasty mathematical derivation, and I'd rather not get that deep into the math. If you like, work through it and prove that it is correct. Gauss came up with this to describe electric fields, but it works for any field with spherical symmetry such as gravity. https://physics.info/law-gauss/
I am well aware of that. I specifically quoted it. It is not that it is improbable to me, but rather that it does not mean what you are claiming it does. Yes, if you condensed the cloud to one body right at its center it would have the same effect on the WIMPs, the problem is that center is going to be a hell of a long way away. Just look at it proportionately; this is a cloud of disparate particles, maybe a handful clumped together, but it is not a solid mass. And it is the total mass of a galaxy composed of tiny specks, so that's going to be a huge size.
I can crunch the numbers for this if you want more solid proof. The mass of the milky way, according to the first result I get on google, has upper bound 2x10
42kg.
Let's adjust for things to make the central gravity unreasonably strong. Each speck of dust is going to be 1kg (obviously really much less) and 1m away from the nearest, just to make the calculations simple. The two overestimations should cancel each other out given they would have opposing effects; 1kg spread out over 1m
3.
So we have a ball containing 2x10
42 points, thus a radius contains about 7.8x10
39 points in a straight line, and so that many metres. So if we shrink all the mass down to one point, all that tremendous mass, we can see the effect it has at that distance. In the same way g=9.8ms
-2 is said to be the gravitational value on Earth under RET, the gravitational constant for something on the outer edge of the cloud is 2.2x10
-48ms
-2.
That is the equivalent to the g=9.8 value, so that is significantly less than that of the Earth, so if a WIMP won't be captured by the Earth it isn't going to be caught up by that cloud. And that's on the edge of the cloud, because that's where the force would be strongest; anywhere inside the cloud and you can't just swap it with a mass at the center because there's dust on the outside too acting to oppose the force from the dust in the other direction; on the edge of the cloud you have the mass of the whole thing pulling in one direction, and even then it is piddling compared to even just the pull of the RE moon, let alone the Earth or the Sun.
Yes, you can argue that it should be less than 1m, and maybe I miscounted a significant figure at some point, but that is a
lot of orders of magnitude to make up for.
The problem is that the distance simply is too great for the mass to exert that much force.
"...given that only regular matter is going to clump (as you say, covering bases, but by conservation of momentum even in vacuum two particles lose speed in any real situation) dark matter will always outspeed it by an increasing margin, keeping it well beyond the dust cloud before anything larger than a molecule would come into existence."
Once again I will bring your attention to relative speed. All the particles in the cloud are moving together as a cloud. If we imagine that the universe burst forth from a single point (just for simplicity here), all the particles in our cloud share virtually the same velocity relative to that starting point. They only differ from one another by a very tiny amount. If we change our reference frame to the center of the cloud as it zooms through space, we see that all the particles are orbiting the center of mass of their cloud. So yes, when the particles collide, they dump velocity within this reference frame and fall towards the center of mass of the cloud. But remember, our WIMPs are staying in pace with that same center of mass that our atoms are falling towards.
The WIMPS keep pace with the initial lone particles; the moment they start clumping, all through the cloud, they'll be outspeeding. Yes, initially you have relative speed, but with no significant gravitational force because, well, they're just particles. You need more of a mass for anything approaching an orbit to be even possible.