You can adjust light source radius in esp files. It's pretty easy to tweak individual light types. However, lights placed in the environment frequently override the default radius in their placement entry, so if you want to do every light source in the game, then it becomes an impossibly tedious approach. Darkening things via ENB or imagespace settings can have the problem of also darkening light sources, since it's a visual effect that's applied to the entire screen. I'm not well versed in ENBs, but maybe this problem can be avoided through careful calibration of the darkening effect. I do not know. I solved a similar problem by entirely avoiding ENB/imagespace darkening and getting my dark nights via darkening the ambient lighting. This is also a tedious process as it means adjusting numbers on every weather type, though less so, since there are no instance entries with overriding to worry about. Anyway, as best I can tell, you'll probably want to dig into your ENB settings to address the issue.