Most people tend to travel through the day, make camp during night. Despite the heat of the desert, it's easier to travel by day since you can see everything, use the sun as a marker and stuff.
B) main reason imo, is that the desert gets cold during the night. Like freezing cold, -20ish degrees Celsius. It's up to you guys how you wanna travel though.
EDIT: Doc also only has two proficiencies. I think that might be from the background?
Choose two from history,medicine, persuasion
2nd EDIT: Apparently I forgot to add background proficiencies. Nomad, you'll get 2 from your background, athletics plus insight. Choose 2 from
Acrobatics, animal handling, history, intimidation, perception or survival.
, concerning Morrigu, I'm not sure if'she's trying to persuade or intimidate