Refering to Whirlybird's original questions (what are you doing flying fixed wings anyway?) : -
1. Yep, Continental engined C150s are more prone to carb icing than Lycoming engined 152s. This is mainly due to the different positioning of the carb.
It's generally not reckoned to be a good idea to use partial carb heat because this can potentially take the air temperature into a range where carb icing is more likely rather than less. Carb icing is most likely when the temperature drop in the carb takes the (humid) air to zero degrees C or very slightly below. If it is well above zero then it will not form ice and if it is well below zero then the ice is less likely to stick to the carb venturi. Full carb heat is nearly guaranteed to make the temperature well above zero in all conditions but partial heat can, in some circumstances, warm the air to the point that the ice is more likely to stick.
2. Having the carb heat on limits the amount of power the engine can produce and in most small aeroplanes (including the C150) allows unfiltered air into the engine. It doesn't, in itself, cause more fuel to be burnt unless you are not leaning properly.
That the air is unfiltered is unlikely to matter when you're high up and away from the dust and debris at ground level
3. I think that this is a common sense type problem (and no - you're not likely to find guidance in a POH). You'll also find that some pilots and instructors are adamant that there's only one right answer, which is strange because the one right answer varies from one instructor to another. I think that you should assess the risk for yourself and decide wether you are more likely to come a cropper from an engine failure on final approach or from a potential slight delay in having full power available on the go around. Personally, with a Continental engined C150 I would consider the possibility of an engine failure at 200 feet to be far more serious than a half second delay in having full power available to go around. When I'm flying a Lycoming engine though my views differ a bit.
You don't, of course, have to turn off the carb heat before applying full throttle to go around. If you do the carb heat afterward then you still got a lot of power during that half second.