MAJOR SPOILERS AHEAD
Maybe I can answer some questions for you, so you can advance in the game even with those bugs :)
1. I don't think getting upstairs is related to love points. You just need to submit to most of Sebastian's request iirc, because you can still have high love points without having his trust (thinking about the pain slut achievement lol). Also, you need to keep a certain amount of sanity or you'll get the "You don't want to leave" ending when Seb allows you to go upstairs. I've also noticed that on some routes the <= and >= symbol are sometimes inverted. Even the sanity value can be wrong sometimes. On Daniela's route, for the ending "Sorry" and "Daniela's Pet", it says sanity > 10, but it should be sanity < 10, but even then it's possible to get the endings with a sanity of 20. So yeah, gotta keep that in mind sometimes I guess ^^"
2. I think it's because your sanity is too low, so you don't want to go back to the basement. You need to make sure it's at >= 30. In my playthrough, when I got upstairs, I decided to go through the basement, but it lowered my sanity a lot and, just like you, I didn't want to go to the basement when I had to escape, which made the timer run out. To avoid that, when you get upstairs, you need to make Sebastian suspicisous. To do so, stay silent when Seb asks you about the food he made and say "No stop" in the bathroom or before going in. Then, when Seb asks you if you love him, just say "Yes" before the timer runs out. Of course, you need to make sure you have enough sanity before going upstairs and before going through the basement to unlock the cupboard.
4. It's about the love meter for the Beg route. If you have enough love points, Seb will stop :). But yeah, it should be shown in the tree imo.
For the "Deal with it" ending, you need to have sanity higher than something I guess. I cannot precisely remember how high it was in my playthrough tho :( Maybe like 30-35? I can recommend to not go through the basement and to make Seb suspicious, then say that you love him. Now, if your sanity is loooow, you'll get "Happily ever after". Once again, it should be show in the tree lol.
5. Punishment = any punishment I think (the candle, the clowns, the claustrophobia, the arachnophobia).
I have the same problem with the screwdriver and the paper clip! Even if I get the screwdriver AND my sanity is >= 60 (i tried lower, just in case the sign was inverted), I can never get "Look for escape" with "Nothing" and "Call for help". I've tried not submitting to Seb and I've tried submitting to him, just in case, but still no "Look for escape".
Plus, just like you, I get a message at some point that I got the paper clip, which I didn't, and I still get the "There is no escape" ending haha.
Hope that could help you a little bit!
