Hey, I hink I can help you with some of your questions.
*2 "Lebenslinie" doesn't mean the "life line" in palm reading. The meaning behind it goes back to Friedrich Hundertwasser. He says that your life can be drawn as a line in the form of a sprial and the way you draw it resembles your true self. And that is quite long.
*3 "auf Gott seinen Nacken" comes from a new slang in the German language. It's mostly used by teens and people in their 20s. "Auf den Nacken von jemand anderem" means something like getting something from that person without giving him something back in exchange at all. It' used like when you buy your friend a beer or something similar. So it mostly appears in a positive context and not in a negative like with leeches.
*4 "sich den goldenen Schuss setzen" only means dying by an overdose on drugs here, but it can be used in a context in which you make fun of how drunk someone is after taking a few shots.
*8 You can see this as an enumeration
"Früher reichte ein Rotwein gemischt mit Tabletten
Heute deep-throate ich Türklinken von Discotoiletten
Es ist nur Rock 'n' Roll, wer K.-o.-Tropfen in sein'n eigenen Drink tut
Und dann Blindflug mit dem Wingsuit
Langsam machen dich Chemodrogen zu Krematoriumasche
Ich renne gleich durch Saudi-Arabien mit Regenbogenflagge
Wer ist krass, he?"
Back in the days he only needed some alcohol and tablettes (which is more or less hardcore in itself) and now he needs more and more of the extremer shit. He licks the drugs off from doorhandles, is nearly dead ("Langsam" -> "Kreamatoriumasche") and "Later I'm running through Saudi Arabia with a rainbow flag" which is considered the most dangerous here. It's a connection to the LGBT stuff there, you're more than right on that. And "krass" really just means "extreme". He's asking the rhetorical question "Who's the most badass here, he?"
*1 - To be clear, rather than "Oh death, she is such a cruel mistress" I think this lyric means something more like "Hey, death ain't nothing but a bitch" - think the "Does he look like a bitch?" scene from Pulp Fiction.
*2 - Apparently when it comes to palm reading there's a false conception that the length of the "life line" on your palm says how long you'll live, but in actual fact ("fact") it only says how healthy you are in general. Or something. This lyric is about that "life line", though.
*3 - This lyric is a bit confusing. The verb here is 'sich gönnen' (to indulge oneself), but "auf Gott seinen Nacken"... I don't have a clear idea what this means. Whatever it does mean, I really don't believe the 'hallelujah' is offering sincere reverence.
*4 - 'Sich den goldenen Schuss setzen' apparently means to overdose on drugs. My first thought would've been that 'golden shot' meant a once-in-a-lifetime opportunity in fitting with the theme of taking risks instead of just sitting at home, but maybe not.
*5 - I was surprised, but the German verb 'ballern' apparently doesn't have anything to do with the English gangsta slang word 'ballin''. The German verb has to do with firing guns in a trigger-happy manner, so it would fit with the Pablo Escobar-style, 'plata o plomo' drug baron life Basti has in the video.
*6 - Apparently this lyric is based on a German advert: 'In jedem siebten Ei...'
*7 - The lyric here is clearly "bareback ficke" and not "Bär wegficke" ('fuck away a bear'... what?) because having sex without a condom is the risky choice that an adrenaline junkie would take - which is also seemingly why he's wearing a Red Bull outfit, because they're the sponsor for lots of risky extreme sports.
*8 - Now, I'm definitely not certain of this, but I swear there must be some connection between the odd previous line about cremation ashes and this one about running with a rainbow/LGBT flag through Saudi Arabia. Minority groups are known to be burned alive in the Middle East (although not necessarily in Saudi Arabia) thus making ashes of them, so... I dunno. It doesn't help that I don't really know what "gleich" and "krass" are being used to mean here, so the actual meaning of these three lines of Alligatoah's verse is very unclear to me. I've gone ahead and written in what I've taken them to mean, but hopefully someone can correct me.