You can use same texture file for multiple models, just dont overlap the UV faces, and you be ok.
But I advise to merge them first, then you proceed to UV. Or else you be struggling with UV scale, also
Try adding some details, and some environment effects. In corridors you dont have much to do, just play with zones of interest, and a lot of repeating elements.
My take on it on the attachment, would play a lot on the lights.
THe infinity seems nice and all, and seems a big thing for MMO`s, but what going to do in games such as FPS, that some models really need to be synced in the same place for everybody?
Had to update the Drivers to get a better FPS, actually at CatBeta15.11, above 60FPS now.
About the models dimming at distance some artistic options can help, like more dense forest and or atmospheric scattering to some fog too.