Your CURRENT annual salary, along with the letter of employment CAN be used to satisfy the concern that your fiance not become a public charge. The I-134 is only ONE piece of evidence that the VO must consider. The I-134 should show your current annual salary of $25,000. I would include a cover sheet which would state simply the time period for the $11,400 (and that you were a student), the current 12 month salary of $25,000, and your job offer and the time period it covers, along with a copy of the job offer itself.
Getting a co-sponsor is a good idea if you can find one, but may not be necessary.
