Subfloor around apron/edge of tub rotted (see photo). As it stands now I ripped out that portion of the subfloor and there is 1/2 inch gap between the apron edge and joists.

The 1/2 inch subfloor only extends 8 inches inward/under tub on each long side.

There is NO subfloor in the middle underneath of the tub!

I am trying to convince my husband that it is well worth getting rid of this ugly yellow tub and putting a 3/4 inch subfloor as required and a subsequent new white tub.

Why would there be no subfloor? Did they not do this in 1967?