[Liam]

I would remove all the foam,it may seem dry but will likely be wet at the bottom against the hull. Looking at you pic i would cut the deck back a little further at the rear to eliminate more of the wet wood that is still around the edges,then fill and seal edges with thickened epoxy or vinylester.(don't use bondo in the marine enviroment).
I would not put any foam back in personally,not good with wood cored stringers.
Keep testing the stringers moving forward until you find good wood,mine were rotten all the way to the cuddy,then sister in at that point.
As far as the sole i would start fresh and not overlay the old deck,way too much uneccessary weight somewhere for moisture to get trapped.
Definitely add limber holes at the back of the stringers.
I am in process of doing the same as you on my 73,i need to update my thread but it is not easy taking pics when your hands are stuck together with resin,lol.