Yet Another Brain Fart -- err, plot bunny

[Necratoid]

I have a lot of Edgar Rice Burroughs books from my dads childhood. The primeval Venus was one of story settings... Always loved the American being interrogated about the distance to and population of his home country. Couldn't stand Tarzan though haven't tried again either. He also did desert Mars.
Anyway, little weird that the inner moon got hit so much or so hard (the Jungle is a smaller moon fused with a large comet) and desert didn't, not impossible or hard too believe just odd.
You might want the desert moon close enough to the jungle to have a Pluto/Charon relationship. If the Jungle moon was knocked into a closer orbit, that after getting smacked around so much by comets that the gravity is from the weight of the atmosphere rather than the core. It was probably in a farther out orbit (smaller ice moon) and its size made it more mobile... then it got close enough to end up dancing with the desert moon.
That would give you the tidal forces from the extra gravity, makes it a it less bizarre that it got hit again so close in. Only have to end up with a bit of a debris field outside the orbit of the fifth moon. That field would also deflect a bit more heat back towards the planet.

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There will probably be a few plants which, like poison ivy, cause blisters, but not everything. Star Trek is not a relaible guide to scientific accuracy.

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I'd argue that point, though that would be more based off of people trying to make Star Trek tech real then it working as is. That and on the spider habitated worlds the planet would have to be more acidic then Earth's. With all that Chlorine hanging around... HCL is going to be far more common. Chlorine takes the place of Oxygen, H20 is replaced with HCL in this case. Unless no plants exist on their worlds at all.
I just can't see it being a case of all compatibilities working out on human off shoots, because they quit being incompatable cold turkey. I can see more cases of human mules or ligers, then flat out viable offspring. Some viable will probably come of the unions, but mostly to me it would be the exception and not the rule.

[Custos Sophiae]

Female ligers and tigrons are often fertile, this after a few million years of evolution. The horse-donkey split is of comparable age. Clearly then, 100,000 years isn't long enough to make full speciation particularly plausible.
The chlorine worlds would be universally corrosive to oxygen breathing life, and vice versa (in the absence of oxygen there would be much more use of nitrogen compounds, which are often unstable against water) but the precursors wouldn't be settling humans on those worlds, only on the planets with a near compatable sugar/protein/DNA based biosphere.
The stars move, of course, affecting the jump points. The precursors are recent enough that this doesn't matter, but during earlier periods of stellar travel the sun's neighbours will have been different. Empires from those periods will have become disconnected, with isolated remants in the solar neighbourhood.
Some of these empires probably also transferred interesting lifeforms to new planets, the same as the precursors - a dozen worlds may have terran grasses - but because of stellar motion the transfers will look near. Two planets a hundred light years apart may both have true cats, and none of the worlds in between.