As to your first paragraph may I suggest that there are two quite different kinds of mental rrepresentation:

(1) that to do with perceptions of things, where, in the case of seeing for instance, the characteristics of the patterns of neural  firing caused by the thing thing seen are attributed by the brain to the thing as its form and qualities. Thus the seeing is about the the thing, and the neural event involved in the seeing, and its associated subjective experience, can in that sense be said to represent the thing. This is to do with intentionality. (This way of looking at it it does involve neural structures in the brain which attribute the characteristics of the neural event to the thing seen, but are quite different to those involved in (2) below). 

 (2) Mental representations of things involved in thinking. Here a neural event  represents the thing in the sense of standing in its place. How can a neural event do that?  By causing the events in the brain which the thing would cause by being perceived. The neural representation which does this cannot of course be a  neural event which was actually involved in a perception of the thing, as in (1) above, for it occurred in the past. Rather it is a copy or derivation of such a  neural event – a mental image of the perception of the thing.  This neural representation of a thing causes other neural events in the course of thinking.