How to Pocket joist into double Wythe solid Brick wall?
The reason the Code does not approve pocket installation of joists and beams is because it is difficult, if not impossible, to install hangers properly in pockets. 

Joists, and especially beams, need to be supported for vertical loading and lateral loading. In order to do that, the joists and beams need to be fastened (nailed or bolted) into a steel hanger and the hanger needs to be secured to the building. Setting the hanger in a pocket does not allow nailing or bolting. (Actually, there are special hangers that extend far enough to allow nailing or bolting, but anchoring the hanger into the wall would be difficult.)

I don’t like anchoring beams into existing 1940 brick walls, because I don’t know how much, if any, reinforcing is in the wall. Rather, I like adding a post to support the beam and then bolting the post to the wall. (Posts under each joist isn’t reasonable, so I’d use a ledge to support the joists, but each joist needs a steel connector to fasten it to the ledger.)

Fire cut joists were used so that the joists would fall out of the pocket in the wall if there is a fire. Now, we reinforce the wall so it doesn’t fall if the joist is burned through. 

There are common hangers that you can use between the joists and the beam by the stair. I’d ask your engineer to clarify the size and type he’d recommend. 

Fastening the ledger to the brick wall will require “through bolts” through the brick wall. Again, I’d go back to the engineer and ask him to design the size and spacing of the bolts required. He will need to design the size of washer to use too so the bolts won’t pull back through the brick wall. Then, use similar joist hangers that you’re using on the other end to fasten the joists to the ledger. 

You asked, how I would have designed the project? I don’t like “Point” connections. That is to say, I don’t like connectors connected into the existing brick wall because I can’t calculate the strength of the wall because the reinforcing is unknown. Rather, I’d build a wood frame wall with all the connections fastened to it in the work area. I’d cover the walls with plywood and then connect the wall to the exterior walls at many locations. The new walls would help hold the existing walls together and make the entire structure stronger.