You lived in a small flat with one bedroom. And presumably only one bathroom.
You had the bedroom. She had to sleep in the living room and had nowhere to keep her private adult things. If they hadn't been in your room, they would have been in the living room (arguably more problematic, esp if you'd had friends over etc).
It sounds very much as if she warned you away from them and did her best to keep it away from you, and you found it through your own, independent actions, going into things you knew were not for you. Which is perfectly normal childhood behaviour, but it's in no way your mum's fault and it's pretty unreasonable for you to be judging her so harshly for this now.
Being naked - you may be uncomfortable with it now, and she isn't/wasn't. Plenty of families are and aren't naked at home, there's no objective right or wrong here. Nothing you've mentioned sounds inappropriate.
Privacy in the bathroom - it's maybe not ideal, but many kids/teens hog the bathroom, and if there was only one, maybe she just needed to use it sometimes when you were there, rushing between her multiple jobs etc.
What you conspicuously don't mention is other men being around - it sounds very much as if she was completely prioritising you, and now you're judging her for having perfectly normal sexual needs that an adult woman has, and managing those in the best possible way that was compatible with raising a child.
A final point - there doesn't have to be blame in all situations. You can feel now "maybe I would have done things differently in her position" - and that's fine, but you can also view her decisions with compassion, and recognise she was likely trying her best, and think kindly rather than judgmentally about her efforts.
Seeing your updates - Why do you feel the need to blame her about the porn videos? Is there something you're struggling to come to terms with about your own decisions in that regard as a teen? Maybe look at past you with more compassion for any mistakes you made when younger as well. It's ok to make mistakes, and learning from them is how we grow. You can regret and learn from the impact of your past decisions/actions without needing to make them anyone else's fault.