Local SEO issue for two businesses in one location

Long story short, I work for a law firm that shares the building with another law firm. We are personal injury, they are criminal defense. When the criminal firm bought the bldg, we added through USPS a "b" designation for our suite # in order to differentiate the addresses with google. We've seen a major drop in rankings since last fall when possum hit, which I know dealt with filtering some of these results, but we are actually two different businesses, with two different addresses, albeit similar. We are getting crushed on local and organic results, where we used to rank in the top 3 for most all of our most powerful keywords, now we're 5-15 on maps, and page 3 for organic keywords. We've resorted to adwords which we never had to do before, and isnt an ideal way to market for personal injury, from an ROI perspective. Diagnostically, When I type the address into google (with the "b"), I get a map snippet that shows the other business "at this location" but not us.

This is compounded by the fact that these two law firms used to be together, doing both personal injury and criminal defense. They then split off, but stayed in the same building. To me this means its even more likely that google is filtering us out, as their algorithm might be more likely to see our previous affiliation and filter us, or at least, is clouding its ability to see us as separate entities.

Short of moving, what can be done to help us differentiate in our location? I made sure our google business categories are appropriately designated (at some point recently, they both auto defaulted to "general practice attorney" so I had to go in and change them back. Not quite sure how long they were both having that designation.

Any thoughts or input would be greatly appreciated. Thanks all