I’d really like to finish this DLC as soon as possible with a new character before facing Benny so I could nuke both factions to get its drops and reset my reputation with both of them.
Is there a way to do it at a low level (below 10)? Even though you have to face strong and aggressive NPCs during the DLC.
It's possible to finish Lonesome Road starting at a low level. I've seen a few YouTubers who managed to do it from level 1 (one example). Some decisions made during this run might not fit with what you want your character to look like at a higher level, so your mileage may vary.
Of course, you don't need to start at level 1 and the base game (or other DLCs) offers enough experience to get to level 15 or higher without confronting Benny. In my current playthrough I'm at level 35 and have yet to confront him. I would suggest side-quests that pit you against the Legion or NCR (I Forgot to Remember to Forget comes to mind) so the reputation from that gets reset as well.
It's another question if you would still be low level upon finishing Lonesome Road, as you gain quite a lot of experience just by finishing the main quests, discovering locations and killing some required enemies at the end.
Theoretically that would put you somewhere in level 8, if you took the "Skilled" trait reducing your EXP-gain.
The Youtuber I linked finished Lonesome Road on level 12, so finishing Lonesome Road below level 10, while theoretically possible, would be an even bigger challenge with further trade-offs regarding the build.
