I don't see how you can get "Harassed" for a DWI.
Nonetheless $13,500 is steep. Does the attorney give you any leeway?
Regardless of how bad your situation is at least you're tracking it and know what is going on.
Best I can say is work with the attorney and state your circumstances.
I don't know what state you're in so I have no idea if a DWI is just being impaired or if it is equivalent to a DUI, but is it worth the money you're spending to fight it? Typically, you either passed the test or you didn't. I understand your job hinges on a clean driving record, but do you even have a chance of winning? Claiming you were harassed won't change test results. If there's almost no chance of winning, I would cut my losses and put that money elsewhere. My wife would take a loan out for me if I asked, but I would never put her in a position where a bad month, week, or day could jepordize her financial well-being. If you're having trouble making ends meet, what will happen once you add a loan payment?
Good luck with what you're going through.
I won't go into much detail here because each state varies, but as hinted above, paying that amount of money to fight a DUI/DWI is 90% of the time, a poor investment so to speak. Courts typically give you a very light penalty for the first DUI such as a few thousand dollar fine, drivers education, and alcohol classes. This all just by signing that you were guilty, made the mistake, and move on. Many many people have unfortunately experienced this, and it's simply the best way to accept it and move forward. (Don't get me wrong, I'm all for defending yourself if it's justified, but likely a DUI/DWI is a clear cut give-me of a case.)
I'm presuming you're already down the road on this thus far, meaning if you are stating the number $13,500 then likely that's for services already rendered and not anticipating. On that subject, all you can do is work out a payment plan with your attorney if possible and hope to put the majority of your funds on items that are Necessary*... things like mortgage/rent, utilities, and payments due to prevent future hits to your credit. A 30 day late is bad, a 60 day late is very bad, and 90 days + is excruciating to your profile.
I'd say, take the the court issue with a grain of salt and move forward, don't fight and waste the money if you truly/honestly/no-questions-asked did drive while under any type of influence. Even in those cases, courts will ask you outright what you can afford the day of the hearing, especially when pleading guilty, and many times openly state "Don't tell me a price you cannot afford, even if it's $25 I'd rather it be a lower number then one you will not be able to make."
As for the significant other being a co-signer, I'm not sure what if any good things could come of that, or if it's even possible with her being in a 600 range. I would do everything known to man short of selling an appendage to stop myself from asking/putting them in that situation. You did a fine job getting out of your previous predicament, continue on that path, achieve success solo and help keep 3rd parties or people you love from being involved in it. Reminder: Most relationships fail due to financial issues... I'd avoid it like the plague!
Good luck, everyone is always here to offer advice / opinions so we're glad you asked!