Ah, thank you, I'm glad you've been enjoying it!
Here's a tip for Ending 4 (I've kept it spoiler free for anyone else reading).
Ending 4 requires you to gain your captor's trust initially, setting up the conditions you need to get Ending 3.
But, in the last section of the game, there's a part where you're asked if everything that happened was your fault, if you take responsbility for your actions. Just like you would for Ending 3, you take responsibilty and reject the idea that you are a tool to be used, but for your next four choices, choose the options that emphasise your individuality rather than a shared connection with your captor (so, for example, choose "I'm more than just [spoiler]." instead of "We aren't just tools." and choose "I'm alive." instead of "We're people.")
You need to get at least three of these choices correct. Essentially you are asserting your identity but not in connection with your captor.
Then, you continue to make the choices that lead to Ending 3, but you'll find that it winds up working out rather differently than before...
I hope this makes sense! A guide is a good idea too, I might have a go at writing one later. Thanks again for playing!