I lost my save file as well, but I was able to download a 100% complete save and use a re-signer to make it work for my game.
If you use the 3DMGAME.ini and the steam_api.dll, you will get a new save file under "1" folder. Drag it over the re-signer.exe to see what steam ID it is using and re-sign the 100% complete save file (or your old save file under "Documents\KoeiTecmo\DOA5LR\(userId)" folder) using that ID to make it work.
link to the save file re-signer and saves:
https://fileshare.steffenl.com/d/ecfdec45fe/
Credit to DiZpel on Steam discussion forums for the tool.