I would like to appreciate for the work devoted to TTW but unfortunately I still got CTD after water purifier and was unable to proceed after main quest.
TTW install was a clean one , Steam version, no custom race(I knew it will be buggy in Broken Steel) no other mods or replaces.
I was able to see all the epilogue of the base game but after loading the game crashes. Tried using NVAC and NVSR but they didn't work. The game freezes instead of crashes.

Clean install with 20.2GB folder and stock load list.
Intriguingly, I also CTD/freeze when I enter some of NV's DLCs. I was unable to enter Lonesome Road (CTD after loading) and Honest Hearts(CTD after slideshow, the terrain/character has been loaded). The OWB was however an exception and was able to complete whole DLC without any problem. But at that time my FNV was modded and I had thought one of the mods caused it.
For Lonesome Road, I will get CTD if I enter the DLC from Canyon Wrekage but if useing console command coc NVDLC04Silo01 can enter the DLC map and able to trigger quest.
I haven't tried any other DLC of FO3 except Broken Steel. I hope to get some help pinpointing where went wrong. Thank you.
