If you get a phosphate kit, I would recommend the Seachem one. It is inaccurate in the sense that it is very difficult to tell the difference between say .4 and .8 . The color scale goes from yellow (0 mg/l) to green (3.0 mg/l) so the way I look at it is if the reagents appear yellow in good lighting then phosphate is at a desirable level. If I see a hint of green then phosphate is a little high. If it is obviously green then phosphate is much too high.

I would avoid the ones from Hagan and Fastest/Seatest as the lowest reading is .2 mg/L which is still way above what you want it at. Don't know about Salifert or any other brands but just make sure it will read down to zero mg/l.

I understand your frustration, my language is usually a little more colorful than "nightmare" when I'm having problems with a tank.