Hi...I'll give you my advice over the years of visiting.
1) 3 days will be adequate as the first day your head will spin and you will likely try to be with any gal that first approaches you. Never tell the gal you have never been before to a FKK, you can say you never been to that particular one..just prime for a set up of being taken advantage of.
Sharks is a very good club these days but can get quite crowded with men, but the gals are definitely top notch for the most part.
Oase is a great club to lounge and hang around, but the girl quality with vary. Every where you go most are Romanian. I would do Oase first as it gives you plenty of room to survey the scene and take it all in. Plan on lots of girls approaching you at Oase so be ready to turn down the first 1/2 dozen or so.
2)There are some hotel options near Sharks, but few as far as I can tell with Oase, Mainhatten in closer in the city and gives you options. I'm always there for business first so I'm always in the city and have to taxi it. Gets expensive...but I figure it still comes out cheaper than the US any day.
3) I've never stayed in a club past 9-10pm mainly b/c I usually have to be up early the next day for meetings, so I'd have to defer to others to comment on the scene after 10pm. But Germany is very safe for the most part and if you're smart and street savvy like any other city you'll be fine. Oase is quite remote near farms so not sure it would be an issue but I can't imagine walking that road.
4) You're ethnicity will barely be noticed since there are lots of Japanese men there and if you're nice and well behaved most won't look twice.
5) Tips are not mandatory and I would recommend against it, but it'll be put to you, I don't think your mileage with a gal will improve if you tip her. She'll smile give you a kiss and be on her way to her next client.
6) I can't speak to this, but since FKKs are legal in Germany I can't imagine it being a big sting target other then making sure the girls have their papers and testing up to date. Not sure where you read about raids, but in the 6 or so years I've been going I've never heard this from locals.
7)There are red light districts like any other city in the world, however, I would imagine it would be pretty pointless, given that FKK gives you all the eye candy you can stare at, and then approach a gal you like and off to room you go!. Why would anyone hit a red light district?
For your first time it will be like a Vegas buffet all you can eat and then you'll eat some more, but eventually with experience you'll learn that it's not so much about getting your rocks off as it will be for the fun of the chase a little bit, hanging out with a gal that has more going on b/w her ears than her legs. When I go (in about 1.5weeks) I'll hit Sharks and Oase or Mainhatten, hang out for about 5-7 hours, relax in the garden with a book, (I never get to read a book these days). Sip on cappuccino, smoke a cigar, watch the eye candy, sleep, get a massage, and hang out with a hot girl and repeat.
My very first trip was to Oase and I fucked 8 girls in 9 hours. I don't know how, but I know I'd never be able to do that again...nor would I.
In the end enjoy, don't be a dick to the girls, be polite to the staff and you'll have a very memorable time.
N.B.
50E for 30min BBBJ/Sex/ one shot on goal. BBBJ with CIM 100E/ Anal 150E...most gals will ask if you want an hour since technically gives you 2 shots. These are standards at the clubs you mentioned.