I had stop cubing for 1 month , Then i come back to practice again for Thailand Championship 2013 . I am now sub 14 O_o (My average before taking a break was 18 seconds)
Try to adjust your tension, I think you lubix guhong is too loose, Mine also had that problem at first but then i adjusted my tension to made it tighter and everything is fine now :) (Sorry for my bad english)
For OLL and PLL i recommend checking other resouces as well so you might find a more suitable algorithms than the one in badmephisto website :) (Sorry for my bad english too)
I got a cash from my friend once too :D He challenged me to get a sub 30 times and i managed to do it very easily (since i am a sub 15 cubers already) Pretty cool story you had :D
I think you had a Rubik's 5x5. Those are bad with lube :) I recommend getting a cube name Shengshou 5x5 and just lube NOT TO MUCH. If you put the lube to much it will make the cube worse. It's call overlube :) I don't have a rubik's 5x5 but those are just regular cube you can get from retail...
FII is a way to go if you don't want to lube it :) It is very smooth right off the box and you can control it pretty easy :) That's just my opinion though.