OK, so I followed the instructions on installation page for TTW v2.7.1a. My load order looks correct(I attached the txt file exported from FOMM). I am running windows 7 64 bit. I have an Intel i5 3.2GHz and 8GB of ram. I am using FOMM v0.13.21.
I make it to the Obsidian splash screen before it crashes to windows saying that Fallout NV has stopped working. When I uncheck the fallout 3 esm and it's DLC I can make it to the main menu, but can't start a game. If I click new, nothing happens. I am also unable to install the optional files through FOMM. It tells me that the main file is not installed, even though I just installed it with no errors and it has a check next to it. I have tried uninstalling both games and TTW and reinstalling several times. I have tried disabling my second monitor, which I needed to due to make Fallout 3 work on its own.
I have the steam versions of both games(fallout3 GOTY edition) and all dlc is installed.
Read the installation instructions more carefully. https://taleoftwowastelands.com/content/alpha-download-v271a#Installation
FOMM 0.13.21 is not recommended. Update to a newer version of FOMM.
The old version of FOMM is not "Large Address Aware" - meaning that it can't address more than 3GB of RAM unless you swap out the .exe file with the one on our download page and you have a 64-bit operating system. Therefore, it struggles when installing large mods like TTW, and usually the result is that the mod is half-installed (your situation) or the FOMM program crashes.
The new version of FOMM can install large mods just fine, even on a 32-bit operating system.