180 lbs of compression is perfect and what that engine would have had brand new. We like to see a minimum of 150 but 140 doesn't necessarily mean you have a major problem. What does the spark plug look like on the 140 side? Does it look a lot different than the 180 side spark plug? Like was mentioned, a leak down test could tell you a lot.
As far as your wiring issue goes, I'd want to check the voltages again with the DSAM plugged in and unplugged but this time check it with the key in the start position. To keep the starter from turning, disconnect the small excite wire from the solenoid before you start your tests. See if you get the same voltage readings as you did with the key in the run position. If the reading you get in the start position are what they should be, I'd start by cutting the diode out of the run circuit wire and put the wire back together without it. It doesn't need it and Kohler took the diode out on the run circuit wire on later models. Or at least check on the input side of the diode and see if your voltages differ on that side. Make sure you get the run side diode and not the start side. The start side diode is definitely needed.