How does Proliferate interact with Exalted and other temporary +1/+1 buffs?
The word 'counter' has a very specific meaning in Magic:


A marker placed on an object or player that modifies its characteristics or interacts with a rule or ability. See rule 122, “Counters.”


so only spells and abilities explicitly mentioning counters interact with proliferate. The 'exalted' ability doesn't mention it:

702.82a Exalted is a triggered ability. “Exalted” means “Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.”

and neither does Hand of the Praetors. So they don't profit from proliferate.