I think something goes wrong when you try to reach their servers from Brazil.And (this if for @Boris): I heard about Enboost Utility, but the link is unreacheable http://www.iparadigm.org/pages/pnenb/ENBoost.html.
I'm able to access this page using proxy.
About textures, I recommend you to use a app called Optimizer Textures: select Maximum profile, Fallout NV profile and resize to 2048 resolution (since you are using a low resolution, there is no point in using huge texture files and suffer). Also, select backup options, if something goes wrong. The autor is also a brazilian, lol
It will correctly compress textures in wrong formats (like DTX5 textures without alpha channel, thus reducing vRAM usage without any impact in quality), create mipmaps (it will reduce GPU load) and like stated before, reduce texture resolution (and that will be unnoticed at 1600x900, so you can safely do it).
If your framedrops are caused by graphic mods, doing this will fix it and give you a smoother gameplay.
Just search for it at nexus pages.
Right now Nexus servers are running like crap here, slow as fuck.