You are leaving out some very key pieces of information to troubleshoot this problem.
1) 2.2 ROM being used include maker and version. (STOCK ROM, 2.2 with root made by Pete FRG01B by Pete)
2) 2.2 Kernel being used include maker, slots, min/max freq and voltage. (2.6.62.9-g103d848android-build@apa26 #1)
3) 2.1 ROM being used include maker and version. (STOCK ROM, 2.1 with root. 2.1-update1)
4) 2.1 Kernel being used include maker, slots, min/max freq and voltage (2.6.29-omap1-g7fa8788android-build@apa26 #1 Build ESE81) .
see above in RED
I will assume those are both standard voltage kernels for the sake of this discussion.
With this information, your testing clearly shows there is a fault in the hardware.
My recommendation is simple. Install the official 2.2 ROM and take the phone into Verizon for repair. Because if you were not rooted, the results would be the same and that would be your only recourse.
If you don't believe you phone is at fault, then find the nearest open WiFi and rerun the tests. If you continue to get these issues with other makes of Wireless routers, then you have eliminated all possible variables and you are back to your phone.
Yea I'm running Stock voltages and CPU speeds. I've tried NON rooted 2.1 also. I had the SAME issue with WiFi not reporting. I called VZW a while back and told them of this issue. They said I'd need to get a replacement. I plan on doing that. I wanted to rule the OS out first. See I OC'ed my CPU a while back and apps started to FC almost instantally. Then the screen went blank. I pulled the battery right away but it must have damaged the WiFi chip. WiFi seems to be working ok other than the reporting of signal. Which is strange.