Obviously, something went wrong in the fabrication of this partial denture. Adjustments are a normal part of fitting a new partial denture, but not to this extent. This situation happens to the best of dentists at times and is probably due to an error in the impression or an error on the part of the dental laboratory that made the prosthesis. Your dentist should re-make the partial denture for you and not charge you. The fact that you have not finished paying on your other dental work is irrevelant. You can not be expected to accept a failed product. Ideally, had the partial denture fit like it was supposed to, there would not have been the need to file down you bottom teeth, unless he informed you before making the prosthesis that this was necessary. Hopefully this sensitivity will resolve on it's own, but ask you dentist about this and he might be able to place a protective coating over the areas that were filed down, or build them back up with a filling material. This should be done at no charge to you as well.
If your dentist is still hesitant to remake your partial denture for you, you might want to make a complaint to your local dental society's peer review committee. They will look at the situation and most likely recommend to your dentist that he re-make the partial denture. A strategically placed word to your dentist that you might pursue this method of action might just solve the entire problem for you. The address of your local dental society can be found here:
I hope this answers your question. If you have any concerns regarding this issue that I have not addressed, please let me know and I will get right back to you with more information.
Sincerely, XXXXX XXXXX DDS