Hi friends!
Am I correct in assuming that this is the correct position for the chainstay tip in the dropout? And the gap should be filled with solder.
Directionally correct in that the scallop is on the inside of frame for chainring/chain clearance but I’m wondering if that bit you have isn’t for the seatstay. Hard to tell by the photos but the gap is surprising and it looks as though the shape would fit nicely over the rounded top of the dropout for the seatstay.