Stepout

Hi all, I am currently playing the Avernum 6 demo and I have two questions. 1. I see you can delete characters in your party. Does it get harder if you do this? Is it possible to beat the game with one or two characters? 2. About the First Aid trait. If I put points into that for one character, will they do first aid to other characters in the party after battle as well? Or just themselves?