Hi,
i´d like to point you to a thread i answered to recently. You have tried so much - but you haven´t tried something which is actually very easy to try - you just have to touch your esxi ;-). So - to eleminate an MTU issue i suggest you disable jumbo frames at esxi level. Just for a short test.
Please also read my statement regarding jumbo frames in general: Re: VSAN "misconfiguration detected"
Best,
Joerg