iPhone 3G - WiFi (and maybe BT) problems

[dj.tuBIG/MaliceX]

Hi all, I'm a recent owner of a pre-owned iPhone 3G and am having some issues.

The device was previously on 3.1.3 with blackra1n when I first received it. Initially I thought the old fw was the cause of the WiFi connection issues, (and of course I wanted to wipe it clean). So naturally, I took the old approach of doing a Restore with iTunes.

Turns out, that was a bad idea.

The phone was originally from the US (I live in Australia), and much to my surprise I didn't know it was unlocked by software, so I did some reading of my own and ended up using the redsn0w 0.9.6 rc19 JB w/ the iPad BB (06.15.00). That got past the pesky activation block (though the battery drain started). Subsequently, the WiFi seemed to have worked....for a short time. The connection issues were still there, either it would scan but not connect, or it would connect but randomly cut out later, or not find a hotspot at all. I've noticed it seems to work when the phone was put on standby for a period of time or shut off from a cold boot.

I shoved on SAM afterwards, to fix the battery drain issue and so far so good, though it still didn't fix the WiFi problems. 3G works fine when I tested, but my current prepaid carrier (Optus), mobile data is hella expensive. On a possibly related note, Bluetooth doesn't seem to like to pair with my adapter...though I'm not too fussed if it works or not. And being on 06.15.00, everyone knows about the GPS kill issue. (Currently stuck since BL 6.2)

I've already tried the following:
-Firmware Restore from 3.1.3 to 4.2.1 without preserving baseband--didn't know how to until now.)
-JB via redsn0w 0.9.6 rc19, plus iPad Baseband + ultrasn0w
-Reset network settings via iPhone
-Upgrade wireless router firmware (ASUS RT-N13U)
-Reactivated iPhone via SAM
-Using WiFi Analyzer to connect and analyze--62% signal strength from the same position as my PC. (Detects the hotspot, but won't connect or would say "network out of range" or "connect failed" subsequently after trying.)
-Setting to Airplane mode and manually connecting. No dice.

I've run out of ideas on how else to diagnose this problem; I'm all ears for any wisdom of experienced owners.

Thanks in advance.