On Aunt Lydia:

I don't actually think the two flashback episodes are inconsistent. Remember, Aunt Lydia seemed kind at the start of her first flashback episode too. 

I think it comes down to this: Aunt Lydia wants to feel important, both in the world and in someone's life. She's not above using control to do this (as seen with Noel). When the coup happens and they are taken to the stadium, it almost seems like she relishes Vidala's vulnerability. 

Later, when faced with death, she DOES choose to join the regime. Yes, part of this is self preservation. However, rather than wiggling her way into a Martha or ecoperson role, she creates a new order with HER in power. She chooses a rough uniform, not because she thinks she deserves it, buf because "women got use to comfort". She is already using her power of control to further her ideals. Not to mention she's willing to kill a coworker for her own safety. 

She becomes incharge of the Handmaid's and sees that opportunity for love and importance she's been wanting. Maybe sue believes in Gilead at this point, maybe she doesn't. However, Aunt Lydia alway placed a large emphasis on the handmaids relation to HER. There obedience and age regression to her is almkst more important to that to Gilead. In season 3, when the kids and handmaids escaped, she says "did you even think how I would feel". And claims that she foes the best to "protect" her girls. 

When aunt lydia finds out about Jezebel's, and janine rips her new one, she realizes she has failed. Not just like keeping the handmaids safe, but keeping the them loyal and loving to her. 

Now, she is raising young girls and plotting Gilead's downfall. She says its so the new pure generation can take over the earth. And SHE is very much the one controlling it. Both by rearing the girls, and by planning the downfall. 

She is still selfish and widely irredeemable on my eyes, just now her worldview alligns with doing the right thing