Ah, you're right on both counts. I'd forgotten about Zhu Jiu getting injured again on the rooftop, and was just thinking of when Ya Qing told him "The bullet didn't hit anything vital, but it still depletes your power." But I just realized that right after that, she says he won't be able to do much "for a while," which does definitely imply that he'll eventually heal from that injury, even if it may take some time. So the injury he got from Shen Wei probably was the more serious one, as you say.

And I somehow totally missed the fact that Dixingren and Yashou didn't diverge until after they arrived in Haixing. I think the subtitle translation of "the other aliens chose to settle deep underground" is what made me think there were already different kinds of aliens before they made that choice, but you're right, the opening lines definitely seem to be saying there was just one alien species when the spaceship arrived. Thanks for telling me where to check!