Floor joist attachment improvements in presence of existing ledger?
Simpson makes brackets that can be attached with joist hanger nails that are NOT joist hangers; I have them on the ends of my stair stringers. Most likley the: 

L/LS/GA Reinforcing and Skewable Angles



I suppose other companies make similar things, though to some extent SST is such a behemoth I don't know of any others in my local market. Anyway, if the ledger is carrying the bottom load, these will provide reenforcing for the attachment.

They also make flat reenforcing plates that could be attach across the splits to stabilize them, at least temporarily (which can be a few decades in house work, often enough...)