1. You got the DeltaModifiers text or excel file in your stats file and delete the lines that give you ability bonuses. If you're editting the excel file, you'll have to go to the "All" file to generate the text files with your changes. See this thread for more details on how to edit stats:

http://steamcommunity.com/workshop/discussions/-1/616198623973649136/?appid=230230

2. At a certain point all item drops are level 1-3 even if you're killing level 8 enemies, for example? That's a weird bug. Make sure you didn't change any level requirements for certain things.

3. You can edit the treasure tables of traders with the treasure table text, in the same way I assume you edited the treasure tables for item drops. Traders generally have specific treasure tables like Cys_Arhu which you can easily add items to. I believe that traders already generate new items over a long period of time and there's code for that somewhere. Just change the timer to 120000 or whatever 20 minutes is in milliseconds.