Yes, use the NPCs on the college sites. There’s some queston whether the CBversion is fully updated to the individual colleges’ formulas.
You can’t just input your numbers, have the bio dad later use his, and expect those two runs to add up realistically. But the NPCs usually aren’t built for a divorce situaton (or self employment.)
And the stepparent is included because he/she makes up a chunk of the ‘household’ income and assets.