mobile

YES, I have read as much as I can in the forums (all day today, rather nice way to spend a holiday though).

I have a Xperia Z1 Compact D5503 handset (FR SFR version, from eBay). I have recently updated it to Android 5.0.2 via XperiFirm tool. I flashed the Customized_IN version (D5503_Customized IN_1281-0184_14.5.A.0.242_R3D). It WAS NOT rooted and I don't remember if I had unlocked the bootloader.

[I have a laptop running Windows 8.1 x64, with latest versions of XperiFirm, FlashTool x64, Android Studio (with Google USB driver), PC Companion. My laptop detects my phone as MTP (or MSC when I choose so), but in the Device Manager, it never shows as android adb device (always MTP, or USB stick). I tried Update Driver option but to no avail, it says the Google USB driver or the downloaded Z1 Compact driver (from Sony site) is not supported (either by the phone or the PC). But the phone shows debugging connected, even prompts my authorization (first time only). Flashmode and Fastboot modes are detected well enough.]

Now, it says I am not allowed to unlock bootloader (via "*#*#7378423#*#* > Service Info > Configuration" menu). It shows the following:
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Rooting Status:
Bootloader unlock allowed: No
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I am unable to unlock the bootloader (or root, yeah, that's the ultimate goal) via the following methods:
1. Official Sony Method,
2. ZergRush
3. TowelRoot,
4. Easy Root Tool,
5. Newroot (by Doomlord),
6. Flashtool (that BLU option),
7. Fastboot via cmd.exe,
8. Flashing pre rooted zip files (cannot open stock recovery option, does this have any? I used the stock recovery a lot on my old Samsung).

Flashtool, cmd and Newroot showed variants of this same error: "only position independent executables (PIE) are supported."
Sony gave me a code, but that also yielded another variant of the same.

Now, as far as I have understood, what I need is one or more of the following:
1. a pre-rooted ftf file (someone said that is impossible as for Sony's encryption, is that right?)
2. some way to root without unlocking bootloader (Newroot does that, but did not work)
3. some way to override that crazy arrogance of Sony and unlock the bootloader and be my white knight...

Can anyone provide me with a guide or some example? It is not at all fair of Sony to create these non-allowance nonsense.

P.S. Please do not mind my tone, I am usually very docile but a whole day (literally; 6 AM to 6 AM next day!!!) in front of my PC without any result have mutated me a bit.
BTW, I am fairly proficient in following complex instructions only if they are conclusive (I don't want to spend another day figuring out how to follow them)