EDIT: To begin with you should probably install adb/fastboot directly from Google. This is the best way to update/maintain adb/fastboot.
So you state that you have no access to the bootloader, yet you are able to issue fastboot commands and invoke at least some type of response? Then that means you have access to your bootloader my friend. Fastboot == bootloader (or Download Mode, which is essentially still bootloader). I've never had a chance to mess with your specific model, but if you're stuck in a bootloop I'd suggest trying to issue a few more commands:
fastboot flashing get_unlock_ability
this will let you know if you can unlock the bootloader
fastboot flashing [unlock] [unlock_critical]
one of these will let you unlock the bootloader (as long as nothing else prevents it from doing so)
And if you're able to unlock it, I'd suggest downloading TWRP for your device (Google = best friend), and flashing it to your phone with a
fastboot flash recovery [twrp.img]
Bricks aren't ever really a permanent mess-up, as long as you can get into some type of recovery. Even if you can't get it unlocked or flash, you may be able to boot still with a factory image (Google = best friend), then try flashing the full firmware, if it wont take, extract the boot image and see if you can force it to boot with
fastboot boot [boot.img]
let me know if any/none of these work and we can go from there. best of luck.