if you feel that having the slush fund stops you, why don't you ignore it? or maybe divide it every day so you would have the same rules as Discover? What I mean is that if you're on 29, I would like you to think that you're on 36pp ad that you can save up to 7 a day towards a night out. This way you wouldn't feel as bad about using the slush fund and you wouldn't feel as if you're eating too much.
I have kept on losing weigh with propoints and I weight 7st 13 (oh well, 8 st now after a week with my sister coming around, but never mind! It's water retention). Hence, you CAN lose weight with propoints and you don't eat too much it's just an impression because you see more points. It's as if you were comparing the prices of a dress 15 years ago (when the old points plan was introduced) and today: something that l15 years ago cost £5 now would cost £9 or £10... but the item is the same! Because the kind of money you're earning now is higher than what you would have been earning 15 years ago, it doesn't make any difference in your purse. But there could be things that 15 years ago cost £3 and now cost £10 and things that 15 years ago cost £10 and now cost £13... so it's all about making wise choices and use your points to the best.
Does it make sense?