SUMIF and lookup function to combine data

these SUMIFs stiil are causing me some issues :o(

i've attached a spreadsheet showing my attempt at a formula and at what i'd like to achieve. what that is is, take data that is found on "sheet 1" at "P" level, extract it and ignore duplicate "acct" lines, and accumulate it into "groups" as contained in a table (hence the INDEX/MATCH lookup without absolute cell reference).

some comments:
-data is 250 columns wide and 300-400 rows so can't use SUMPRODUCT as i can't physically define every range on "sheet1".
- the relationships may change hence the table on "sheet3".
- the data can not be aggregated before it is copied to "sheet1" yet must be aggregated when displayed on "sheet2".

thanks in advance - i think i'm partly there yet also think i have a long way to go.