To use nails you need to buy a 'Hammer [WIP]' from store, and click LMB while holding a hammer to place a nail (you need to have at least 1 nail in your inventory)
I don't know if amount of light turned on affects the transformers, but it probably is, i've seen several videos of other people playing the game and I think people who turned off the lights needed to fix the transformers less frequently, but it may be just a coincidence
Increasing the level of drives increases their cost:
Most signals cost 5 for level 0, 10 for level 1, 15 for level 2 and 30 for level 3
"Garbage" (noise) signals cost 20 for level 3 and same for levels 0, 1 and 2
Some of event signals cost 30 for all levels
Some rare signals cost 0 for level 3 but same for levels 0, 1 and 2
Repeating event signals (these mostly have small size around 0.25 MB) cost 0 for all levels