Echo was never destined to stay. Losing Fives, sustaining the torture he did... his ability to safely form attachments was destroyed forever. Only Rex will ever have full bond from him, because Rex came before he lost everything including his ability to attach. His skills, drive and ethics outstrip the work the Batch does post defection, and he isn't particularly impressed with Hunter's decisions. He outgrows them over the course of the show, and leaving them was inevitable. It doesn't mean he doesn't feel deeply, and truly, for the Batch members and Omega, it just means they were brothers before him, and would be after. Tech had Echo figured out in the end. It was just a truth no one wanted to hear.
Wrecker suffers facial pain, neck pain and headaches from his accident, including his own migraines from the TBI. Radiating neuralgia and jaw pain sometimes causes weakness and/or numbness when chewing (meaning he doesn't always like chewy or crunchy food), and he also lost some teeth, leading to his slight slur. He looks kinda wonky when eating, earning him even worse bullying from regs. But he never tells Omega when its Mantell Mix time.
Tech made the decision to Plan 99 himself because he had a back up plan... which he didn't disclose because he wasn't sure it would work. The whole scene only makes sense if that's the case. I don't need to say it, but CX-2 is deffo Tech, and the only way that makes sense is if said plan *did* work, and he *did* survive, but was captured before he could re-join the Batch and skedaddle.
Crosshair *needs* direction and structure, his "bigger picture", his purpose. His belief in CT99's superiority is really a desperate clawing for meaning in the face of constant abuse and alienation, and that meaning only exists so long as the Empire does. That's what he meant by "This is who I am." in the s1e15 ending, and what Tech means when he says Crosshair's immutable nature is "severe and unyielding". And in spite of his own desires, he's not cut out for leadership and shouldn't be anywhere near it, and he proves that over and over. He's an excellent strategist and a piss poor judge of character, and that's ultimately what he comes to understand through meditation.
Hunter's migraines significantly reduce on Pabu as his life becomes more routine and he gets more regular sleep. Away from flickering lights, sharp chemical scents and high stress situations, the chronic pain he lives with melts away, and some of his anger does too. Not all of it, pain reduction is no panacea for C-PTSD, but it helps.
Omega, and we the audience, deserved a better class of snack than candy coated popcorn.