Might I suggest a few minor changes?
Ditch the foam underlay, it will cause more trouble than its worth. Track is best glued down IMO, to a good FLAT base, cork or I lay mine straight onto the board. Use a contact adhesive to glue it down, not too much in case you have to lift it in future but a good bead on the back of the track and on the board will hold it, put a few books on top to hold it in place.
Ensure every section of track has a separate power feed to the DCC bus. This can be done with droppers or wired fishplates.
How old is the track? Recycling has its limits if you want good running, old flexi track can be more bent than it looks and points over 20 years old, especially insulafrog types are crude by comparison to modern ones, and will perform accordingly.
Screws are only suitable for carpentry, they have no place on track, for the reasons you have outlined!
Well done on the split chassis conversion, hope the remaining chips stay un fried! Maybe a forum posts in "modelling questions" with pictures of all the problem areas of track will yield more knowledgeable help than mine.