Is it easier to answer "B" to all of those questions than it is to think that Yoda's "size matters not" was not a statement of scientific fact that meant "capable of generating infinite numbers of kilowatts the Force is" but might have been a deeper statement regarding an aspect of the nature of an ill-defined pseudo-magical mystical force.
He was replying to a specific suggestion by Luke that the ship was too big to move. In this case, the specific aspect of the force that allows for telekinesis is not "ill-defined" with respect to the size of the objects that can be moved; because he clearly states that the size of the object does not matter.
I never implied Yoda didn't mean what he said, it just don't think he meant it as a literal claim of unlimited telekinetic power. Or at the very least, perhaps size does not matter to the Force, but individual Jedi have limits, most apparently far less than Yoda.
Obviously individual Jedi have limits, as evidenced by Luke's failure to fully lift the ship. However, Yoda made the claim and then demonstrated the claim; which establishes that size doesn't matter to Yoda's use of the force. There were many opportunities for Yoda to do some heavy, decisive moving in the PT and he didn't bother. Why not send the droid armies flying? Even if he had to do it in X-Wing sized sections of weight, that's likely a few hundred droids at a time.
I would argue that the films give us very little clear understanding of the nature of the Force. Why does an energy field generated by all living things grant telekinesis? Why is Watto immune to the Jedi mind trick just because he's greedy? Why does doing evil turn your eyes yellow? What is the nature of the 'haunted' cave on Dagobah? How can you move fast enough to block a blaster bolt but get caught with a little rope thing from Boba Fett?
That's irrelevant, because the aspects of the force in question here, are the ones that are defined (through dialog and/or example) well enough for this discussion.
But, if my options are either every Jedi in either trilogy are hopelessly stupid (including Yoda, who made the claim you're hanging this all on) or that the understanding of the Force you propose is somehow incorrect, Occam's razor points me fairly clearly to one of these options.
You're missing the point. Yes the examples imply stupidy on the part of the Jedi, and the writing is to blame for it. Write it so the power isn't unlimited, and write scenarios that can realistically pose danger despite the powers-as-defined.
(ps. I wasn't 'begging a question'. At the very worst I might be accused of suggesting a false delimma.)
There was no false dilemma. You were begging the question. You were assuming that the Jedi couldn't have been [written as] morons (which is the question), thus Yoda must not have meant his statement literally. You can't assume (beg) the question in order to establish the conclusion. You need to give actual evidence of your claim that Yoda was not being literal, because without that, it is simply a case of bad writing; and bad writing tends to make characters look like idiots by default.