One additional item that came to mind, I recall reading something on aftermarket metering blocks used with an incorrect metering block-to-main body gasket on the primary side.
It left an exposed channel that leaked fuel on the passenger primary side.
Maybe you've got a similar problem since you say the front left mixture screw gets unresponsive....that would be the side that could get the same open channel leak path. Plus it ties in with the general wetness you are finding.
IIRC it leaks to either exterior or the power valve vacuum cavity, or both...?
Something to look for, anyway...