I think you want a query like this:
SELECT f.GROUPPRODUCTTYPE,
MIN(j.CREATIONDATE),
SUM(case when j.INVOICEDATE < '1990-01-01' then j.GROSSEXCLVAT else 0
end) as Product1
FROM SC_JOBS INNER j JOIN
SC_FRAMES f
ON f.JOBID = j.JOBSID
WHERE j.CREATIONDATE BETWEEN :StartDate AND :EndDate
GROUP BY f.GROUPPRODUCTTYPE
ORDER BY min(j.CREATIONDATE);
It replaces the subqueries with conditional aggregation, based on the invoice date.