I feel like the author might benefit from reading a blog post that was posted on HN a while back[0][1], specifically the "two and done rule" and the "do it anyway principal". Yes your manager is wrong, but the way you handled it is very immature. There are "shit" managers everywhere, if you get one, suck it up and start planning your escape. If you really want, you can go higher up the chain and raise your concerns. If your concerns are dismissed, just drop it, there is nothing to gain by fighting.
I also think that you made mountains out of mole hills in some situations. The time estimation "catastrophe" wouldn't even phase me. I'd just say some very high number (3-4 months) and if they weren't happy, I'd just reply "when we start working on it we'll do our best to pull it in". Yes it sucks that you have to do that, but you should really learn to play the game, at least a little bit.
[0] https://madned.substack.com/p/an-old-hackers-tips-on-staying...
[1] https://news.ycombinator.com/item?id=28141203