You only need to total your points when you post a project. You'll want to keep a running total, usually set up in your signature line.
You do not have to do the daily challenge on the day it is assigned, but you get 10 extra points if you do. Also, you can "stack" daily challenges and use multiple days on one project.
Each challenge is a "one project only" challenge - you cannot take points for a daily, weekly, or monthly challenge more than once.
When there is an option - like card/layout, or this week's half-week challenge, you need to choose one of the options, not both. In other words, it's an an either/or choice, not both/and.
I think I got all your questions answered, but if not, ask another one and I'll try again. :-)
Nice to have you playing! Newbies are always welcome here!