For the save game bloating (which could be the reason for the crashes), you might want to try this mod:  
[**Clean up** by kuertee][1]

> **Description**  
> Prevents saved-game file-size bloating by cleaning the game of actor
> and item references that are no longer required. (e.g. inactive
> references created from dropped items that were picked-up by the
> player.)
> 
> Cleans long-dead actors that may have been corrupted somehow.  

> **Details**   
>The cleaning process used is the game's inherent behaviour of
> removing items that no longer has any "links" to the game world.
> 
> Normally, dead actors and "dynamically created" items that were not
> picked up by the player will be removed from the world, when the cell
> they are in resets. (Dynamic items are those created at game-time as
> opposed to those created in the Construction Set. Examples of these
> items are: those created by PlaceAtMe, those dropped by the Player,
> those dropped by dying NPCs: e.g. shields, etc.)
> 
> However, there are cases when these actors and dynamically created
> items will (for some reason or another) stay in the game world
> forever. And actors not cleaned up by the game properly will never
> respawn, causing a "broken" game experience. Saved-game bloat is the
> result of these. And saved-game bloating may be the cause of some game
> crashes.

To prevent crashes, I'd recommend [**Streamline**][2]'s Streampurge feature (memory purging on an intelligent, scheduled basis - can be configured to do a memory purge before a save, which can help with stability; [more info here][3]) and [**Fast Exit 2** by Scanti][4]. You can choose to enable only Streampurge and Streamsave and not the other Streamline features in sl.ini.

If you are running a 64-bit OS and have 4 GB or more RAM, you might want to try the [4GB EXE Patcher][5] on Oblivion.exe (not sure if this is also the EXE name of the Steam version). Discussion about this on the Steam forums on [this link here][6].

After installing any new mods, make sure to run [**BOSS** (Better Oblivion Sorting Software)][7]. BOSS properly sorts the load order of the mods, avoiding crashes and mod conflicts. It also provides a large number of usage notes for many mods, including requirements, incompatibilities, updates and bug warnings.

More info on configuration and mods that can help stabilize and prevent crashes in Oblivion here: http://tescosi.com/wiki/Oblivion/Stabilization_and_Optimization


  [1]: http://www.tesnexus.com/downloads/file.php?id=24606
  [2]: http://www.tesnexus.com/downloads/file.php?id=10400
  [3]: http://www.oblivionmodwiki.com/index.php/Streamline
  [4]: http://www.tesnexus.com/downloads/file.php?id=22410
  [5]: http://www.ntcore.com/4gb_patch.php
  [6]: http://forums.steampowered.com/forums/showthread.php?t=1308967
  [7]: http://www.tesnexus.com/downloads/file.php?id=20516