Hi Ratath.
Thanks for your praise. I appreciate your comments and suggestions.
I going to update sheet but first I have to get my hands on SCAG and get some free time

Also I'm waiting for provider to enable my internet access. I recently moved to another city so now my only internet time is while I'm on job
Regarding your requests, unfortunately I can't add another field for third class. I'm limited by this design. I didn't created this design and I don't have source files.
But I can suggests that you custom insert two classes in second class field.
Example:
For Fighter 3/Wizard 2/Rogue 1, in first class field select
Fighter enter level
3 in class level field for first class. In second class field enter
Wiz 2/Rog 1 (don't use dropdown) and in class level field for second class enter
3 (notice that this is a sum from other two classes) so that sheet can correctly calculate total character level.
I'm sorry but better than this I can't do for now.
Point-buy method is not limited to 27! If you enter 15 for all ability scores, you'll notice that info field says: "You have spent 54 points!"
But ability score is limited to 15 max. I can remove limitation and set to, lets say 18 for ability score.
Hope that this resolve your problem with point buy
P.S. If you like this sheet I would ask you to rate it (that little green arrow). Thanks