Here some more information to check into:
https://www.repairprocedures.com/servic ... 17196.html
This site may have more information for a price. "Subscriptions start at only $5.00" and that is for 24 hours of access for what looks to be GM factory on-line manuals.
https://www.ar15.com/archive/topic.html ... &t=1037159
The guy here has info on troubleshooting the fuel gauge and he clams to work at a GM dealership. Follow "badhammer" info for troubleshoot and that is probably all you can do.
http://ricksfreeautorepairadvice.com/gas-gauge-wrong/
To somewhat back up the above link with the guy who works a GM dealership, this gives a general layout of how newer cars fuel gauge works.
I have read other posts about changing out dash cluster in Matrix (Vibe) and in most cases some part of the cluster does not work after the change. It needs to go to the dealership to have the cluster pulled and sent to the factory to be programed for that vehicle or something like that. Anyways, it does not look like anything cheap. Your ohm reading looks good and if you have checked all the connections and wiring to and from the tank, then it looks like the next stop is the dealership. Like I said before - good luck to you.