You claim that "endogenizing" political behavior excuses political malfeasance. I am not sure that it does. I think it exposes politicians and teaches us what rules or constraints contribute to a continuing problem of the political economy. Ignoring it, as you seem to suggest, is just as bad, if not worse, and certainly would not lead to the "policy design, political leadership, and human agency" that has been lacking. The fact that these things are lacking in the political sphere is reason this discipline was conceived of in the first place. Moreover, not all theories of the political economy neglect the power of ideas. But it is true that for the vast majority of political actors that private interests and re-election are paramount.
You use the words "ethical standard" with little clarity, and I think with little justification. First off, there have been a number of campaigns where the richer candidate outspent their opponent and lost. This is not to say that money does not wield a level of influence, but it is not the sole determinant and arguably will matter less as costs of information spreading decrease.
Insofar as ethics are concerned, there are a minefield of concerns with spending caps on campaigns. For example,if a candidate pays money to a publishing company to publish a book where their political views are outlined, is this campaigning? If it is, are you ready to claim that this speech should be suppressed if the candidate has met their spending limit? What if someone else feels compelled to campaign for them? Should they be limited in their speech under the spending cap?
Your distrust for the Citizens United ruling is evident, but you don't address the real ethical problems underlying campaign spending and speech.
However, I will agree that campaigns could use a bit more substance. But that is nothing new.
Criticizing the Ecuadorian government and Assange for their selective (mis)use of the rule of law seems like a good way to foster popular dislike. However, in view of the current situation, this seems like ad hominem critique- the rule of law should come in a case by case basis, in which Ecuador's "dubious record on freedom" and Assange's "brand of populism that cloaks itself in the rule of law" is irrelevant to this merits of this case.
It is curious that these rape charges conveniently came as the US was pressuring its friends to freeze Wikileaks operations and assets. It is a clear that these charges may be contrived as state powers use any and all means to arrest Assange and stop Wikileaks.
You can criticize Assange and Ecuador for being inconsistent across time, sure. Irregardless, however, of whether you find Assange hypocritical, in this particular case, the extent of US influence and methods to track down someone it simply doesn't like and completely arrest their actions with seemingly trumped up charges seems a bit Orwellian.