A corrupted save is something different than a save that cannot currently be loaded due to version related issues. If you saved the game during the brief period that version 1.1 was released for the Xbox, you're now in a situation where the game cannot be loaded because the 1.0.3 version of the game doesn't understand the save format. Taleworlds already stated that the game should be usable again once 1.1 is re-released for the Xbox.
For that to happen Taleworlds first needs to identify, fix, test and then publish a patch for the issue - which i assume is their current top priority by a large margin. To actually get the patch in the hands of end-users they will then need to submit the patch to Microsoft, who also need to certify and actually publish it. This in turn adds some time overhead a developer has no control over, which is probably the reason why taleworlds cannot give a specific ETA.
Asking for a refund for a product you already used is very likely going to be a lot more trouble than is worth it. You can ask the place where you bought the game for a refund, but if you've owned and used the game for a long time its unlikely the request will just be granted. Legal options beyond that tend to be quite the headache, and most jurisdictions i know require granting a vendor a reasonable timeframe to solve an issue. (And no, a reasonable timeframe in that context is unfortunately not the arbitrary amount of two days you've set yourself).
Realistically i would advice just playing a different game for a couple of days and then checking back. No matter how many statements you make on the forums or how many deadlines you set: it is not going to have any influence on the time a patch is actually released. Unless doing so works as a catharsis for you, save yourself the time and frustration and just have fun playing something else while this mess gets sorted in the background. Afterwards you can hopefully just continue playing your Bannerlord save where you left of, if you feel inclined to do so.