Yes you would launch all commands from the platform-tools directory and it sounds like you're doing that. Your results are a bad sign I'm afraid. It's a semi-new, yet increasingly common phenomenon I call the Lollipop fastboot brick. Basically speaking, it means you can write fastboot commands and the phone recognizes that you did that, but it won't process them.
That is bad and it's almost certain that the tool won't work for you either while in this state. There is a way out of this but it's not fun. You're looking at this:
http://forum.xda-developers.com/lg-g2/general/lg-g2-unbrickable-fix-real-hard-brick-t2904404
What you do there is short some specific capacitors on the motherboard to invoke qhsusb_bulk (9006) mode if you are lucky. Or QDLoader (9008) mode if you're not quite as lucky...though both can be fixed. 9006 can be fixed using either Linux or once again, the same tool LitrosNub posted earlier. You'll note it has a bulk mode fix option in it. If you end up in 9008 mode, you'll have to post back and I can walk you through that.
At this time, you would be well served to install the Qualcomm USB drivers to your machine. Get them here:
https://dl.dropboxusercontent.com/u/7460142/Qcomm_Drivers.zip
Having those installed will greatly help you to determine if you end up getting 9006 bulk mode or 9008 QDloader mode. You'll eventually determine this by watching Windows Device Manager while performing the shorting of the motherboard. Those drivers allow much more specific info to show up in device manager. For reference, 9006 bulk will look like a bunch of "drives" in Windows. Those "drives" are actually the partitions and thanks to a security breech which has since been patched, you can interact with them and via superuser, you can reflash them to restore the bootstack similar to what I mentioned earlier (aboot, boot, dbi, laf, rpm, sbl1, tz) which will once again restore download mode.
Sorry man, this particular phone has become quite involved in it's brickability. The good news is, it can be fixed if you have the patience and some willingness to open up the phone and do a small amount of surgery. As you can see, you'll need a small screwdriver to access the motherboard. Many jeweler's screwdriver sets don't have a small enough phillips to do the job. If you have a set which contains a flat blade 3/64", it will work to loosen all the screws.
It's a lot to take in so read up as much as possible, then ask if questions. I've been through this several times on this phone and other LG's containing a Snapdragon so I'll assist where I can.