If I replace the missing files with those from one of my act 4 saves, it crashes trying to load. That implies the different language versions are incompatible, one or more recovered files are corrupt, or both.
Unfortunately, the missing files are also a problem. The data.000 file contains all the information about your characters (level, stats, skills, etc), as well as all friendly and enemy NPCs. The story.000 file contains quest information, and the world.x0 file information about the game world (levers, locked/unlocked doors, walls, quest opened locations, etc). I'm guessing the inv.i1 file keeps track of the inventory in containers (its size roughly doubles after entering the BF, when lots of containers get added with the dungeons). If you have to replace the data and story files, you might as well replace the whole save.
This may just crash trying to load, but here is my save at the end of act 3
(4.3MB). If it works I can find a save closer to where you were in the game.
If it doesn't work, in a new game it is relatively easy to hex teleport to the stairs that are the exit to act 1 (boosting your level, etc, appropriately and maybe hex teleporting behind the counter at the citadel armoury to pick up some equipment). You could either do the quest to get the summoning doll or do the inventory file swap procedure. There are a couple conversations you would have to have in act 2, but you may be able to skip most of it using the inventory file procedure to get the ingredients for the cure and then hex teleport to the alchemist. You need to do a number of quests in act 3 to trigger the encounter with Kiya, so couldn't avoid redoing stuff there.
You could try just making a copy of the Bd_act4_start folder, and then hex edit it to boost your level. You'll also need gold to buy equipment from the BF merchants, and learn skills, etc. You can also hex edit to enable skills or increase the level cap (if the trainers were in areas you skipped, etc).Hex editing - gold, experience, stat/skill pointsActiontrip.com's Beyond Divinity Cheats
- starting a new game with stronger charactersTeleporting anywhere (via hex editor)