English prepositions are tough, and you're right to zero in on them as being worthy of a lot of study. They're particularly interesting because they seem almost arbitrary, until you examine them carefully, when they reveal a lot of the subconscious/conceptual-metaphoric thought processes that underlie our language use. Metaphors We Live By is a classic in this field & would probably be instructive, if you have time for a little light reading.
As to your specific questions:
on the month ⇒ for the month
I do not perceive a difference here. "On" appears in this context pretty frequently in the financial press, and might(?) be more precisely referring to an exact monthly period, while "for" just means 'over the course of the month', but I think they're equivalent.
of 0.2 percent ⇒ for 0.2 percent
An estimate of x percent means "in the amount of x percent". "For" would not have that meaning here; "for 0.2 percent" would be used in a context where you were providing an estimate for a 0.2-percent segment of some population or quantity. Something like "It may be bright and sunny, but today will be a terrible day for the 0.2 percent of beach-goers who will be attacked by sharks..."
sliding 0.3 percent ⇒ sliding by 0.3 percent
I don't see a really strong difference here, but I would prefer the first in this context as it sounds more formal, more mathematical. Other speakers might well disagree. If you were speaking of something somewhat less abstract, there would be a difference: "He slid the door 3 inches to the right" is good, "[x]He slid the door by 3 inches to the right" is weird. Note that this is particular to verbs which take a quantity: "[x]He missed his target 3 percent" is weird, but "He missed his target by 3 percent" is fine. (Of course, you could also say "He missed his target of 3 percent", which just means that he had a target, the amount of the target was 3%, but he didn't make that--no information on how much or how little he missed by.)
a median estimate in a Bloomberg survey for a decline of 0.1 percent ⇒ a median estimate by (from) a Bloomberg survey of a decline of 0.1 percent
"in" vs. "by/from" -- "in" identifies the location of the estimate. It may be found in the Bloomberg survey. "By" emphasizes the agency of the source, or stresses who is making the statement. "By" would not be appropriate here, since the survey isn't providing the estimate (it's the analysts who responded to the survey who are the actual agents). "From" could work, but that emphasizes less the location of the estimate than its general origin--a distinction which I am sure sounds vague... I think the difference between "in" and "from" here is that "in" is very precise: this is the source and the location of the estimate, and if you go to the survey, you will see this estimate in it right there on line 12. "From" means that the survey was the estimate's ultimate origin, but it does not precisely locate the estimate as something contained within the survey: rather than a number cited directly from the survey text, there could be an interpretive process to arrive at that estimate, say... I am splitting hairs, a bit; let me just say that "in" in this context sounds more precise and more formal. (Also "in" obviously could only be used for a printed or text source. You can have an estimate "from Bob", but to have an estimate "in Bob" would need surgical intervention!)
"for a decline" vs. "of a decline" -- The distinction I'm seeing here is that if we said "an estimate of a decline of 0.1 percent", that suggests that we're estimating something that has already occurred--we haven't measured it precisely, but we estimate that there was a decline and its magnitude was 0.1 percent. An estimate "for a decline of 0.1 percent" suggests (along with the context) that this is a prediction. We are locating the uncertainty as being about what will happen, rather than the magnitude of what has already occurred.
Though thinking it over carefully, I think the author might have been more precise to say "compared with a median forecast" or "compared with a median prediction", or "expectation," etc.
In conclusion, prepositions are very hard, and there's a lot of variation in the understandings of even native speakers when it comes to these very subtle nuances of meaning.