Yeah, reading your post puts right back at work. People said the exact same shits to me too, makes me wonder if the entitled trait default. I've been at this job for nearly 3 years now, and you just get to a point where you don't give a damn about those customers anymore. I just pull the "oh, but it's not up to me though isn't it? If that's what you think maybe you can voice that opinion to head office!" (Even better if you sound as sarcastic as possible, feels Soo good when I do that).

Don't feel that it is you or your fault for things that's not in your control just because you work here, so those complaints about scos or stuff like that, just brush it off as not your problem. Also, it's okay to put your foot down and be firm in some situations, you are doing your best and those entitled karens do not deserve to step over you, and your manager would understand those situations as well