I am sorry to hear that your girl has stopped grooming herself, has a wheeze, has a sensitive lump in her jaw and that she paws at her mouth after eating, but I am pleased to hear that she is still eating.
The most likely causes for her symptoms are related to the lump and include an abscessed tooth root, a bacterial or fungal infection in her jawbone, or a tumor in her jaw. I suspect she isn't grooming because it is painful to do so.
I understand that she is not easy to handle and your finances are limited but this is not something you can help her with at home. She needs to see a veterinarian for an examination, sedation and radiographs of her jaw as well as collecting a biopsy and samples for bacterial and fungal cultures.
This may be a tumor given her age, but if this is an infection we need to get her on medications as quickly as possible. These infections can take months to resolve when they involve the bone, and the best chance of success is treating as soon as possible.
If a regular veterinary clinic is beyond your means financially now your other option is to contact your local shelter or humane society and see if they run a low cost clinic or know of one in your area.
If not here is a web-page that lists some that may be able to help:
Other sources of help can be found here: http://speakingforspot.com/?p=Financial%20Assistance%20for%20Veterinary%20Care
In the meantime feed soft foods, add water or broth to her meals to make sure she takes in enough fluids, and try to help her groom by brushing her.
Please let me know if you have any further questions.