Help with xperia arc s LT18i downgrade to android 2.3.7

Hello, my name is Andrew.
I recently got an xperia lt18i phone.
For free.
this is my first touchscreen smart phone thingy.

I would like to install a nice ROM on it, as currently it has problems connecting to WiFi.
Known issue i was told.

Currently it says:
Android version:
4.0.4
kernel is:
2.6..32.9-perf
Builduser@buildhost#1
Build number
4.1.b.0.587

My main problem is that i can not find FTF files that i could flash to it, to enable root hacking and unlocking and so on.
Mostly every link is dead i find.

Could someone help me where could i obtain a root-hackable FTF file i could flash ?
I can use the flashtool app, no problem there.
I managed to allmost brick this device as i found only 1 FTF file i was able to download,

sxperia_arc_s_lt18_4.1.a.0.562_nordic.FTF
afterwards the thing was unable to start.
So i searched and after a few attempts i managed to find
LT18i_4-1-b-0-587_Generic Global World.FTF
file, i managed to flash it, the device works, but WiFi problem remains.

What i would need is a working link for an older FTF file that can be root hacked by flashtool. Then i will need to unlock the bootloader, i found the tutorial for that.
The other thing i would need to obtain is a custom FTF file that has WiFi fixed.
I can find download links for files like that, but they are dead links.

So please, if anyone has proper and working links for downloading:
root hackable FTF file
worthy custom FTF file

I would be thankfull.

Thank You for reading.