Is there a way you can reset challenges?

Some of them do reset automatically each time you finish them and some don't.

I need to reset "Lead Dealer" and "You Run Barter Town".

Neither of those reset. http://fallout.wikia.com/wiki/Fallout:_New_Vegas_challenges page shows all of the challenges for New Vegas and shows which ones are recurring.

I did not know about the console commands and Steam thing so when I earned those 2 legit, I did not get the achievements in Steam, so is there any console command to reset them so I can re-earn them? Also I will not create another character to do them again.

I don't know of any console commands that can reset challenges, they might be out there, but i don't know them.

Those two challenges are pretty easy to do with an average Guns/Scavenger playthrough. If your dead set on getting them then you could either dive into Google to try and find the command or do a Gun/Scavenger playthrough and not think about it until you get near the end.

I just finished my fourth or fifth playthrough and there are still a few challenges I haven't gotten.