What is the diameter of the water line on the 642 sub zero

If you tried using a typical 1/2 to 3/8 faucet connector such as https://www.homedepot.com/p/3-8-in-Compression-x-1-2-in-FIP-x-20-in-Braided-Polymer-Faucet-Connector-B1-20A-F/100459572, and it didn't work then ignore this answer, else...

Plumbing pipe size can be misleading due to the fact the pipe diameter is based on outer diameter and the inner diameter varies with wall thickness. To determine standard pipe diameter you measure the outer diameter and subtract 1/8".

The typical 1/2 inch pipe has an outer diameter of 5/8" and like wise a a 1/4" inner diameter pipe is a 3/8". So likely the typical faucet connector is correct. But you may have something unusual so FYI.

CLEAR DRAIN LINE, VERY COMMON PROBLEM - TRY TO PUT SOME TUBE INSIDE AND CLEAR EVERYTHING OUT OF THERE. I USE 1/4 " TUBE. HOPE IT HELPS

This is either the defrost sensor or the main board. Neither of which you can do anything about with no parts. https://www.repairclinic.com/RepairHelp/How-To-Fix-A-Refrigerator/55-114-539299-/Sub-Zero-Refrigerator-not-defrosting-642

It is your evaporator fan. When the door opens power is cut to the fan motor.

I have the Sub Zero 650. I am not sure if yours iworks same but what you do is use a 3/32 Allen wrench; as you push the handle into the screw on the door so that it is flush, you insert the Allen wrench in the hole at the bottom of the short vertical connector at top and tighten; repeat for upper or lower part of handle.

it's condensate from the evaporator coils. when the humidity collects on the coils, it should drain into a pan under the fridge that gets evaporated from the hot-side line. check to see if the condensate tube from the coils is still in the pan.

remove the crisper drawers and you will see a drain trough and a drain line . One or both is most likely blocked. If you pull the drain line off the trough usually you can clear it with a turkey baster filled with hot water

Yes, this is normal.  My 642 does the same thing. It seals to be more efficient while trying to cool back down after it has lost heat while open.

If the seal or seating area is sticky, wash it with warm water. If it isn't, this is just the sign of a good refrigerator. As the air cools, it becomes more dense and creates a vacuum inside the compartment. With a pliable new door seal which is sealing well, combined with a large door, this can cause a great seal with alot of pressure pulling on it. Smile, this is why your consumers bill will be much better with that new sub-z.

Call the factory at 800-222-7820 for the manual. It souns like you are missing one or two screws. Pull the ice tray out and lift it up about an inch and it should release. Take a look at the ice maker and there are two supports that both need to have screws on them. There is also a third underneath on some models. Insert the screws and you should be fine.