Hi Troll, several points with varying pertinence. Your joint selection is not anywhere close to optimal for maintaining beam strength, look towards horizontal tenons with diminished haunch. Second when I want to estimate the capacity of a notched beam I think of the beam as a composite of rectangular cross sections with respect to the vertical aspect, in your case the strength of a 2 x7 plus 4 x 10 plus 2 x 7. Third, I would consider whether the ceiling structure could be converted into an attic floor by a future owner.